Why is LessWrong not an Amazon affiliate? I recall buying at least one book due to it being mentioned on LessWrong, and I haven't been around here long. I can't find any reliable data on the number of active LessWrong users, but I'd guess it would number in the 1000s. Even if only 500 are active, and assuming only 1/4 buy at least one book mentioned on LessWrong, assuming a mean purchase value of $20 (books mentioned on LessWrong probably tend towards the academic, expensive side), that would work out at $375/year.

IIRC, it only took me a few minutes to sign up as an Amazon affiliate. They (stupidly) require a different account for each Amazon website, so 5*4 minutes (.com, .co.uk, .de, .fr), +20 for GeoIP database, +3-90 (wide range since coding often takes far longer than anticipated) to set up URL rewriting (and I'd be happy to code this) would give a 'worst case' scenario of $173 annualized returns per hour of work.

Now, the math is somewhat questionable, but the idea seems like a low-risk, low-investment and potentially high-return one, and I note that Metafilter and StackOverflow do this, though sadly I could not find any information on the returns they see from this. So, is there any reason why nobody has done this, or did nobody just think of it/get around to it?