Atrenta have run an interesting survey on the use of social networking by engineers (think LinkedIn, Facebook, Twitter, blogs etc). There is nothing specific to Atrenta or its products (apart from that they put the effort into the survey).
An annotated version of the presentation is on semiWiki (itself a sort of social media approach to EDA) here. Not surprisingly, the most heavily used resource is LinkedIn, followed by Facebook and then Twitter.
Today everything and everyone is connected and crowdsourced. In fact, all social media, from blogs, to forums and wikis have a profound impact on how people communicate, search for information, and make decisions. Research clearly shows that people who share knowledge and personal experience via blogs, forums, and wikis can influence 40-60% of all visitors to a specific course of action. More and more, people will get product information and direction from independent top influencers rather than getting it from vendor sites, advertisements, or other biased sources. Not surprisingly, engineers like to read posts by other engineers and are not keen on video or debates (probably because the information density is relatively low).
For vendors, social media is no longer an experiment or a moonlighting function. Social media is now an integral part of corporate communications. Unfortunately, vendor direct blogging, tweeting, and forums are all sunshine and no rain which limits the credibility. Vendor direct social media is also all talk and no listen (not crowdsourcing). Social media is all about crowdsourcing and that is just not possible on a vendor specific site.