Another factoid to consider - I know of a company that has a Class C that they don't use. To my knowledge, nobody has ever even asked that they give it up. Some automated email process could do this without much effort.
Well, almost. The IPGR robot is, in fact, doing just that.
Based on never having received such an email and knowing of several others who haven't either, I disagree.
"All in good time my pretty..." We are working on the 192.x.x.x swamp right now. Rough estimates (with much more accurate data @ NANOG) 60% - invalid or missing contact information 25% - in use & unwilling to renumber 15% - willing to renumber or return This is from ~6,000 delegated entries. If all goes well, we can find some new area to work on sometime in later this year. Have any suggestions? 198.x.x.x? The old /16 space? --bill