Acceptance of change.

I would say in the BIM workflow (AEC is the business); still a young technology.

lacks of communication between softwares, so many files types.

promote the use of IFCs.

a total lack of understanding by many in the construction industry of what BIM means. The term is like a floating mirage and if you asked 100 people what their definition would be, you'd get 100 different answers.

-Lack of 'standards'.

-Proprietary systems & attitudes.

This was a problem with CAD, it is a bigger problem with 3d / BIM. There is just a billion different ways to do everything.

In the architecture field, the biggest problem we have had with BIM is getting MP&E to jump aboard. There seems to be a good number of structural engineers using BIM but the MP&E engineers, at least in our part of the world, continue to fight the switch. It makes coordination a problem.

Forgive the language, but this is a direct quote from one of my Revit Mentors:
"You have to give a **** about what you're modeling"
Too many people have bad habits where they just want to fake something in "Because it's quicker"
That may be true if your end product is the drawing, but if the end product is a building, it's NOT quicker to draw it wrong.

Dave what do you mean by faking something?
As far as i know most efficient way is to make hybrid model. Modeling basics + more to have right measurements + hatch patterns and materials, then you can draw missing things with drafting tools in needed drawings. Because it can take a lot of time modeling smaller things such as fascia, gutters, battens and many more. I do not want to model everything because its really time consuming, even railings i drew by linework ( yeah i know it sucks) but to make custom railings, families would take three times more time than i draw by drafting tools.

Yup, they would the first time. But let's do the math here:

You're going to work a lot of years with Revit. Let's say that in ten years from now something else comes along and you switch to another software, leaving your built library obsolete.
Let's say you do a lot of custom work and maybe reuse 50% of your families, and you reuse them 1-2 a year.
We won't take into account the profit you gain from reusing families and change them into something new.
We won't take into account the fact that especially fascia's gutters, etc are going to be used a WHOLE lot more (there is only so much types of those).
We won't take into account the possibilities in parametric modelling of those families so that you can create an enormous variety of options with just a few families

50% of the families are reused 2 times a year, during 10 years = 20 times. So, 100% of the families is reused 10 times (on average).
You are now 3 times faster, let's say one hour instead of three hours to create the family. BUT you'll have to redo this EVERY TIME. Instead of reusing it 10 times (for each family) you'll have to spend another hour.

In 10 years, each family you do NOT model will have cost you 7 hours. Remember that we stated you did a lot of custom work, so on average you "draw" about 10 families per project. You do what, 10 projects a year? So in ten years you'll have lost 700 hours just redrawing lines.

btw: also not taken into account: the ability to do facility management, use the model for renovations and stuff. Those simple lines will come back and bite you in the ass. My guess, the actual amount of time you loose with each line you draw in Revit is 3-4 times higher than assumed in the above. Which means in ten years from now, you'll probably have lost a whole year drawing and redrawing lines...

EDIT:
DaveP is correct: at least the same amount of time is needed for extra coordination, so that's another year of useless time...

Let's say in the next decade, there isn't going to be a piece of software worth switching to. Statistics tell us, the probability that you could reuse a family only gets higher over time. Simply because it becomes more and more likely that you encounter a similar situation. So the potential loss of productivity increases exponentially after more time.

Take a moment to wrap your head around that. For me, that is one of the big BIM problems: the incapability to look into the future and think on the level BIM requires. You are no longer making drawings for a building permit. Or for a contractor. Or for a nice picture to show your clients. You should approach your model as the contractor does the actual building. Your model gets the life expectancy span the building has: 50 years or so. Act accordingly. Your contractor isn't going to use inferior materials cause well, it looks the same for the first two months and we'll see after that (or you need a new one, lol). He's going to put his heart and soul into creating the best building under the given circomstances.
It baffles me that a lot of people advocating BIM won't do the same and practise what they preach...

Thank you Martijn, you just saved me 15 minutes of typing (and math!). That's pretty much exactly what I would have said.
Bango, here's a few more examples:

• I can't tell you how many times I've heard someone say "It takes too long to make a family, so I'm just going to draw lines". Invariably, I'll hear back from them - or even worse, someone else on the Project team - a couple of weeks later. "Why doesn't this equipment show up in my elevation?" It's just lines!
• "Why didn't this Door show up in my schedule?" It's just lines!
• "I changed this Casework on the Plan, but it didn't fit when we built it" It was just Lines on the Floor Plan. And more - unrelated lines on the Elevation!
• We had one other person who - rather than use the Linked Structural model - "just drew lines". The Stair towers did not get coordinated between Architecture and Structural, and caused a $10,000 construction change order.

Perhaps my favorite, though was:

• "I don't care about 3D Walls, so I just drew lines." Then they redrew the lines as Room Separation Lines becasue they needed Areas and Room Tags. Then they had to put in little short Walls because they needed Doors. By the time they were done "just drawing lines" it took at least triple the time. All because they started out thinking "I'll just fake it becasue that's quicker."

Yes, some things can take longer to model properly that to "just draw lines". The drawings may look fine, but drawings are NOT your end product. The building is your end product, and THAT's what gets better coordinated and better built if you "Give a **** about what you're modeling"