Is anybody doing this for investing? Couldn't you use social media to track when people join or leave a company and determine whether the company is healthy based on the quality of the employees it employs using their estimated net worth, market value of their house, where their kids go to school, etc.?
I do a talk called "social media for social evil" where I talk about these aspects.
When I advise companies working on a major new initiatives and hiring for those, that they ask employees not to update their Linked In for a few months, don't mention the company on social media, etc. It means competitors are slower to see the change.
I suspect you'd get more noise than signals trying to plug the quantitative data into a model of changes at a company given the data is likely patchy, outdated and not infrequently mistaken identity. It might offer more useful qualitative insights when the investment being gauged is a 30 person startup, but you'd probably get just as useful information from manually trawling the employees' LinkedIn pages...
