I think people who use the social network sites for themselves, not thinking about the business of it, will just be annoyed by the adverts.
One of the great things about social network sites was that they were free from the advertisers, all you got was the view of the people using it.

I do get the point that this also shows that social networks are more prominent now as advetisers are willing to pay to be on them. But do strongly feel people will be ennoyed by this...