eWeek (May 19, 2008) published a survey on Web 2.0 deployments and plans for such technologies among enterprise IT managers. The population was somewhat limited (282 individuals) but it made some interesting findings.
It's apparent that the current deployments focus more on internal staff than the needs of the customer.
Blogs (49%), wikis (48%), and RSS (43%) were listed as the most deployed technologies. Social networks come as the forth technology (27%) but was viewed with some level of concern.
Security (41%) and concerns for leaks of sensitive company information (35%) were listed as the two top worries when pursing these technologies.
The article correctly concludes that there are no particular security concerns with these technologies. They add some complexity and a few new attack techniques will probably crop up but, while security concerns may be warranted, is it a more fundamental matter.