If it's just one piece of spam, with very few few people on-line it can takes about 15 minutes before it's finally taken down, but on busy days, it takes about a minute and when we man the spam stations during a big spam wave, it takes about 2 seconds to get flagged into oblivion!
#;-)
###So keep on flagging! Eventually the spammers will give up!
No, they won't: there are always new spammers around that don't know that they shouldn't even try to spam here...