I'm with Liela on this one. This guy didn't bump just one thread or post just one ad. It was 4 or 5 when I logged on last night. One is enough.
But for the sake of your comment, the difference is that it is spam and not even allowed on most forums. The other Undergrounds like this one have basically become totally inactive and have nothing but spam ads taking over their front pages.
Most of the time, no one here objects to the occasional ad, especially if it comes from an active member. A polite and informative thread introducing themselves that tells us about their service is usually welcomed with questions and even recommendations from members that may have used the services before.
It becomes spam when (like in this case) an advertiser bumps 4 or 5 (sometimes even more) old threads to the front page just to promote themselves. In cases like that, I wouldn't even consider using that business, just out of principle.
Whether you or I like the front page chat topics isn't the issue. As long as the topics are within the TOS of this forum they are not abusing the purpose of the forum. On the occasion someone decides to troll the forum and bump numerous old threads one after the other, the mods usually ice that user.