Ah, this may help explain why so many sites have +1 buttons while they get so little use (often on the order of 1% of the Facebook Like activity). So Google us

Ah, this may help explain why so many sites have +1 buttons while they get so little use (often on the order of 1% of the Facebook Like activity). So Google uses its search monopoly in such a way as to incentivize site operators to advertise its social network (in the form of those buttons), which encourages growth of its social network — and as a separate issue, allows them to track people, be they Google users or not, across more of the Web. No anti-trust issues here, move along... </sarcasm>