2
You should be fine if you or your family/friends don't click on your ads. Keeping an eye on your stats and being aware of your normal click activity is always good in case you notice a huge jump at some point.
As for Google waiting until the $100 dollar mark before disabling accounts ... that's a possibility. I've read about it happening quite often so maybe there's something to it. Whether the publishers were innocent or not is another matter. I tend to doubt it.
Unless you have a huge amount of traffic, don't expect to get rich. You might make a little something at first and then comes the smackdown (aka: smartpricing).
Oh, and don't join click scams or put AdSense on an account that's been banned (like a website you've purchased or a domain you've just bought). But don't expect Google to tell you if the site has been previously banned because they won't. It's all a big (guessing) game and guess who has the advantage?
[size=x-small]Working sites:
XOOPS 2.0.16 PHP 5.2.2, MySQL 5.0.24a-standard-log, Apache/2.0.54 (Unix)
XOOPS 2.2.4, PHP 4.3.10, MySQL 3.23.58, Apache/1.3.33 (Unix)[/size]