Personally, few things rile me up like a manager giving me directives to 'evangelize' products to my family & friends on my personal social accounts. I am currently in this situation. I have no problem evangelizing on social accounts tied to the company (the company's official twitter, facebook, etc.) or writing posts on the company blog, but I do not use my personal social accounts for company business and don't plan on doing so in the future. Maybe I'm just old, but I need a separation between my business and personal life on the web.
I'm sure the techs who keep the servers running in the Google data centers love having 25% of their bonuses tied to social products they may truly dislike, don't use, etc.