You are %100 correct in that many of these consumer focused Web 2.0 companies will be in for a very big shock when they try to make the move to Enterprise 2.0

Jeremiah Owyang had an article up earlier this year about the difficulties in selling into the Enterprise and how they underestimate the extreme complexity of selling to the enerprise

http://www.web-strategist.com/blog/2008/01/14/10-considerations-for-the-startup-planning-to-become-enterprise-20/

My comment in that article was that the only consumer focused Web 2.0 companies that will make the transistion succesfully will be those that have a dedicated Enterprise Sales Team and those that have other revenue streams to tide them over while negotiating with prospects during the long sales cycles.