Solutions to class assignments don't generally "increase human knowledge". The only people they will be useful to are students looking to cheat.

A lot of people on BoingBoing were saying that the prof should generate a new assignment each time: that's really not realistic (pg mentioned this in on of his essays). I've just finished the first year of a CS degree, and I can see the advantage of having assignments that have been set for multiple years: they're more 'polished' IMO and better able to stretch actual CS skills and not just the production of boilerplate code.