The D&D targeted AEG supplements from Evil and afterwords use this approach. Unsurprisinly, Mearls also contributes to many of those books as well.
I personally think its a good idea because it speaks to the underlying flexibility of the d20 system. There are poeople out there (see the d20 star wars argument on the d20 system game forum) who seem to think that if it is not spelled out in the rules, you can't do it. Seeing this sort of thing everywhere should help open the eyes of GMs to the fact this ain't a boardgame, folks.
It also helps cut down on skill proliferation. Too many games out there try to tack on new skills every supplement. Unfortunately, some d20 system authors still engage in the practice, which water's down the potency of skills by dubdividing their functions and forcing characters to divide points between closely related skills. Take a look at Forbidden Kingdoms. It has charm, conversation, and bribery (which, in my mind, overlap with bluff and diplomacy) and investigation (which to me, overlaps with search and gather information.) To me, you are better off making new skills of these things than new feats. Frex, an investigation feat could give you +2 to search and gather information roll.
Feats => extend the hell out of 'em
Skills => be wary
