I'm sure DD is right about the future; keep it spam free and keep building quality stuff... much of google aim during their recent turmoil must have been to identify spam, cloaking & redirecting and they are sure to get better at it as time goes by - like xxx jay said - it will not be there forever.
I agree with Alphawolf & Plateman too - there are cheaters in every industry but the adult industry (like the drug industry) attracts the worst of them, always has (on the basis that nobody wants to admit they were cheated when trying to buy porn or drugs) - but things are happening to tip the scales (pop-up blockers and better se algos) they will make it less profitable and the scumbags will move on to easier pastures...
And best of all remember - for every surfer who thinks like Alphas friend, there are a few hundred thousand people turning 18 every day and hooking up to the web
