Yep... I've seen people come here or to WhiteBlaze and instantly post and their very first (sometimes, only) post is to sell something or push some commercial website or transaction, book, DVD, etc.
And to make it worse, they sometimes cross-post to multiple threads, which just makes their "spamming" worse.
Most rules have a history behind them and are not adopted just for fun.
As others said, don't take it personally and the 50 post threshold is easy to reach, if someone is here for the right reason.
"You can stand tall without standing on someone. You can be a victor without having victims." --Harriet Woods