This question has crossed my mind several times. signature campaigns must have paid out hundreds of BTC's by now,but how much profit did they generate to the hosters? what do you guys think?
There is no guarantee that signature campaigns will give profits, but it is how marketing and promotion works. Site's owner needs to promote their site as effective as they can in order to get visitors. There were some signature campaigns last year, just alive for less than a month. It means that their signature campaign was not profitable for them. But there are also some signature campaigns that running for long time, it means that that the signature campaign is still profitable (at least still give positive effects to the site)