I dont know why is for somebody annoying if forum have signature campainsg allowed.That is good for forum users and users which come just to advertise their site.So the are in position win-win and forum admin is in win-win position because forum is more popular.
The majority of the problems with Signature Campaigns are the things that stem off of them. If you give someone an incentive to post on the forum then it is guaranteed that some people will take advantage of this, spamming the forum with useless shit.
This benefits no one but the spammer. It ruins the forum experience for a number of users, and paints the company incentivizing this posting in a bad light for allowing it (Ex. YoBit, CoinRoll).
I hate when rich peoples are moving ref link code
Because once again, it encourages spam. This forum (Especially subsections such as Micro Earnings and Gambling) would become a cesspool should ref links be allowed.
In regards to the original post, I believe that the main problem with spam stems from there not being a clear point of what is and isn't allowed. You would think that threads promoting said spam would be disallowed under the 'No Insubstantial Posts' rule, but apparently not.
If you want to ignore the majority of these posters, I would suggest
DannyHamilton's ignore list. While it does sometimes block posters with constructive posts, it is a fairly good compromise to avoid seeing spam.