Most of the web is spam and porn so is it really that surprising? ..
I knew someone many years ago who had started to make a living out of link/ad farming, and this was back when dialup had not long been around where i am..
Few years later he was doing the same thing, although much more involvement in the XXX related link/ad farming, and making even more income. In any case the procedure was always the same, and as far as i know, has changed little even now.
The problem as i see it, is that sites are being rated or chosen based on search engine rank (usually google), and that's never been a reliable way to determine the validity or quality of a website (sure google would have you think otherwise of course), but it's the most common means to finding what you want, and by all means why would you want to look through 100 pages of results if the first page has what you want ...
When you talk about developers and the tactics they use for search positioning, i think it's important to remember, the good/legit guys, the people that adhere to the (shall we say "preferred") way of getting their website indexed and found are actually part of a minority, and that's not very likely to change, no matter how much wishful thinking we might do .. we've been in the minority for a long long time already ..
I've seen several users post here asking questions for sites that look like they are being used for link/ad farming (it's quite evident when you've seen it before), but then i'm not here to judge them on it, as it's not really a WordPress issue ..
In reality i don't believe the web is generally a place of professional conduct, as much as we'd like it to be...
All the same, i do agree with you Daniel... ;)