14 DAY TRIAL // I call "spam" any unwanted message I get. To me, it makes no difference if it's related to penis enlargement, cheap drugs or botsent invitations to some site or religious/political messages. Unwanted e-mail is annoying and I hate it! When you've got a lot of people in your contact list you get[admark=1] a lot of invitations to sites. I get a few weekly, and it's not that my friends deliberately send me these messages - it's bots that sites have. Once you make an account to a site, a EULA that nobody ever reads will pop up. In it, the owners of the site will eventually state that everybody in your contact list will receive an invitation.
I get lots of such messages. Though sending them is legal, I, just like a lot of other people think they're spam. Now, let me tell you how money comes out of this. Sites that offer free social networking services live off ads. So, basically, they're selling their public for profit - but that's an older technique they learned from the media. Let me explain - media products are the only products sold twice at the same time. Take a paper for example, it is being sold to you (the one that bought it) but parts of it had been sold to companies that wanted their products/services advertised. Having a large public means they will get more money out of ads. Same thing goes for sites too.
The more users visit the site daily, the more companies will pay up to have their products advertised on that site. So, basically, these guys are sending all those unwanted invitations to attract more users, thus making more money. It's simple and profitable! Further more, if you will join such a site, you are bound to get a lot of messages daily, about new features, new widgets and stuff like that, just to make you visit their site once more. The more clicks/day they get, the more money they make. So, that is how, in an indirect way, unwanted messages lead to legitimate profit!