With BIM, project collaboration was possible. But online collaboration over CAD drawings hasn’t been easy yet, with some applications that work very slow or in a limited way.
As you can see on the above video, sharing works on a very simple way over email allowing people to work on a drawing at the same time. I gave Autodesk Butterfly a try at their technology preview website (no need to sign-in, just hit Try Now) and the flash interface loaded fast. It is very intuitive to use if you have used AutoCad, and the version control system allows you to go back to previous states of the drawing.
An iPhone version would be great, as it would allow you to do on-site review and annotations. Anyway, the preview looks very strong, and maybe we will have a full version of this tool available soon.