Also they cannot be remembered just by keywords as there are number of sites with small change in domain name.
IMHO if it's not immediately evident, memorable and typeable then it's not worth it.
I have quite a few names that are very trade specific generic names such as colourwidget or widgetproduct, trades people refer to these items in this manner and they have no problems in recalling them however trying unusual spellings or other "designery" type stuff generally fails however there are the exceptions...just can't recollect one right now!