No offense taken. 2 comments, though:

1. fofou.org hosts the forum for my SumatraPDF site, which is 33,279 in Alexa. I think that's enough of a target, more than most forums out there.

2. I don't think it's productive to bring top 1000 websites into this particular discussion. OP's forum wasn't that popular and most forums, by definition, won't be either.

Once you're there you're playing a completely different game and at that level you should have resources to win it. I don't see spam on Wikipedia, StackExchange, Quora, HN etc. When there's will, there's a way to fight spam.