I still have my CRC.
Yes, professors who write their own textbooks are rather a mixed bag. There are a few who do it to fulfill a real (or at least honestly perceived) need, but I have to admit I'm rather suspicious of the practice in general. I particularly had trouble passing Differential Equations because the textbook we used was written by the professor, and he wasn't a very good teacher in either format.
There are a set of subjects that do need constant updating, of course-- and wikibooks would probably be a better choice for those, because the turnaround time on textbook publication is so slow. For the rest, I'm convinced that most new textbooks are generated either because some faculty member wants a subset of several existing textbooks to cover a particular course as it fits in the department's curriculum (see above proposal to combine chapters of e-textbooks) or simple greed.
