Ok, as I see many people here are defining SPAM different as some ppl think one topic is SPAM other think it is not.
For me SPAM is commercial advertisement.
Here is the official definition when searching on google for "SPAM":
"... Spam - Unsolicited "junk" e-mail sent to large numbers of people to promote products or services. Sexually explicit unsolicited e-mail is called "porn spam." Also refers to inappropriate promotional or commercial postings to discussion groups or bulletin boards. ..." (Source: http://www.getnetwise.org/glossary.php )