I can understand the space and hard to sell part, especially regarding old computers - once they're older than 5 years at most they are regarded as useless to most.
The privacy thing is always blown out of proportion. Like the Goodwills here, just take out or erase the drive and off you go. Found several early 90s machines without a HDD.
Still, common sense should be used. I just got a Performa 6400 at a pawn shop... And wow. There were about 30 floppies, all filled with personal data, about the most I have seen in a conquest. Taxes, IRA data, business data, family history/stories, two disks labeled "memoirs"... Pretty bad. It's a good thing I'm not the type to take advantage of that, it's all you need to become this person really.