There is an unwritten social contract between we the punters and social networking sites that make money by data-mining our activities and targeting ads at us.

That contract is essentially that we will let them have our personal data in return for cool services.

So far this has gone rather smoothely for both parties.

Google with its “You can make money without doing evil.” seems to be the poster-child for this relationship.

At first people were weary, even paranoid about putting personal information online, but this has relaxed as we dipped our toes into services and found that nothing really bad happened.

Bad things did happen, but it happened to other people using other services.

Trust has grown and people have moved into these sites in droves.

As long as the services didn’t cross some invisible line and offend or scare us personally it was all pretty good.

Maybe the worst that could happen is that the site would secretly stab you in the back and sell your email address to a mailing list, fine – my spam filter just works a little harder.

Now Facebook’s Beacon which tells your Friends what you have purchased online, seems to have crossed that line – the social network equivalent of “What happens in Las Vegas, stays in Las Vegas” no longer seem to apply.

Its not like Facebook are stabbing you in the back privately, they are doing it in a room full of people and broadcasting it on a loud hailer.

It seems that people are noticing.

Facebook is targeting people who are active on the net, who trust the net to make online purchases.

If you imagine what the heuristics of Beacon are to maximize ad audience, those targeted probably have a larger than average number of Friends they can complain to, so I suspect the maths is against Facebook on this particular feature.

Now a Facebook group has been created to fight it.

Hoisted by own petard I think.