> then the sites in question can simply choose not to enable it
Google can reduce the page rank of websites that dont enable it (or just not give any page rank at all) and now everyone who wants to be found has to enable it
>>rvba+(OP)
That would clearly be an antitrust violation or deceptive business practice in one or more countries. Though by the time they get penalized for it, the damage would have been done.
>>rvba+(OP)
Google can already do this if they want to. For example, they could increase the page rank of sites use Google Analytics (or any other Google client library). But this would be exceedingly stupid because it would compromise the quality of their search results, and remaining the leader in search should be their highest priority.