When last I worked in web development I worked with some fairly unscrupulous people who would use every method known to them to boost page rankings, including some rather obvious cheats. They even got one or two of the sites they built banned from engines, much to their clients annoyance, but the client was able to appeal and ultimately got it fixed. Is this common practise? And how easy is it to get banned, how often are cheats caught?
I ran a black hat experiement with about 10 domains. During the short duration of their life (2 months) they received a ton of traffic. But after 2 months they were banned by Google. So Google does do a good job taking care of most black hat techniques from what I can tell and from what other people told me what happened to them.
Everyone is trying to cheat Google. The biggest cheaters get penalized sometimes. However if you do a search or two you will see there are still plenty of sites ranking great and providing no value at all.