Yahoo! has recently started mailing out keyword promos reminding people to bid up the most competitive holiday related terms. Those are probably good words to steer clear of paying for. Many ignorant bidders jumping into the market at the same time creates an ugly overpriced playing field, although if you can sell them their PPC traffic the overpriced bidding may be a beautiful thing. Keyword terms with a large standard deviation may create good arbitrage opportunities.
Advising you to steer clear of industry-recommended buy lists applies equally well on Wall St. See Aaron's article for more detail on what a "large standard deviation" is.
The main things holding the PPC keyword market back from being a full NASDAQ-like marketplace are:
Later this year, when Yahoo! changes it's PPC model to look a lot more like Google's, the standardization aspect will get a little bit better.