Just read this thing about the spammers. I will never understand why someone would join a forum they don't have interest in just to trash it.
If you really want to know....I'll tell you.
In a word (well, 3 words) PAY PER CLICK (or, better known as PPC)
Certain web sites (mostly sites that sell something) will pay you for every person that you direct to their site (they pay more if the person actually buys something). It's fractions of a cent per click but it can ad up.
It's the idea behind banners on some web sites and phone apps.
So, let's say that I, as a computer programmer and a coder want to make money in PPC. But, I don't want to do it the long way with banners and legitimate means. I just want to generate clicks
So, I write an application (actually, many people would call it a virus) that goes to forums (by list or at random) and makes a post that has a link to one of my advertisers sites.
I send this little application/virus out on the internet and like a spider, it crawls all through the web. Logging onto forums and leaving posts with links to my advertiser's sites.
A well written app like that might make 10 or 15 million posts before it runs it's course.
If only 1% of those people actually click on one of my links.... how many PPC's to I have.
See why they do it?
And, think about it... how many people here actually clicked on one of those links before really thinking? I'll bet there's more than a few. LOL
It's all about money. Isn't it always.
Here's a link for more reading if interested....
http://www.wordstream.com/blog/ws/2013/01/09/ppc-faq-for-beginners