Now I have learnt a new thing today. I thought deeply one day why don't the companies that promote their businesses or casinos here pay heavily to Google instead. I couldn't get any direct answer, here I have gotten a clue.
Then I now have a question; does the signature we wear in the forum has any promotional or visibility effects outside this forum?
It increases SEO (search engine optmization).
As bitcointalk.org is a very strong domain with lot a of visitors it has a high rank in Google searches. Links from such a powerful domain increases the rank of those domains.
So, a good campaign, might help the promoters website to get a better position in Google searches