Micro sites or macro site?
While I have and do respect Jill's experience, I sometimes think she is getting a little too set in her ways and not flexible enough to allow for exceptions.
I too agree that in general, it is better to focus on one site and not a lot of small ones, but there are times when small specalized sites can and do make sense. A small site with lots of information on one focused topic should generally do better that a larger site that covers many topics.
In fact there is a trend by some large companies including Geico (Cavemanscrib.com]) that use a small site to create a specialized that that does one thing, but does it really, really well. In this case, I think that a micro site strategy can make sense.
But all of the concerns that Jill raises are very valid, and there are others as well. The amount of resources needed to build, promote, and maintain many small sites are generally going to be much greater than one large site.