I have not seen any sign of spam, and the advertising is a pain. But both the site and the forums are free. Imagine the complaints if THG decided to charge even $10.00 a year to participate.
Get real... name one site that actually makes you pay for their forums. No spam, though, just ads out the ass these days. I'm not really complaining about the ads, though... Tom has to pay the bills somehow. I guess that reselling all those free testing components isn't paying off on Ebay... lol