They were salary dumps, one way or the other. Take for example the Marquis Daniels deal -- he was hurt, and we wanted to clear his roster spot. We could have waived him, but would have had to still pay his salary (and I believe the luxury tax implications of it.) While that wouldn't have been the end of the world, the Kings agreed to take on his salary for us, in part because they were under the minimum team salary threshold, and needed to pay someone something. But you can't trade something for nothing, per NBA rules, so the Celtics needed to get something back -- hence a protected 2nd round pick that was effectively nothing, since no one really expects the Kings to be in the top 5 in the league anytime soon. Obviously the Kings and Celtics have been doing these kinds of trades for years, and now the Celtics have a lot of these picks. I'm fairly certain they could turn around and trade them to some other team if they were on the other side of a something-for-nothing deal, so they have some modicum of worth if we want to take on a player being dumped, and don't want to give up anything for the privilege (since our picks are tougher to protect based on us winning.)
The pick from Cleveland (which I believe is really Minnesota's) on the other hand, is a real pick, isn't protected, and should be at the beginning of the second round. Everyone complained about the Erden-Gody deal for nothing but roster spots, but that pick has actual use, and at least under the present CBA, is at least as valuable as one of the last picks in the first round (because 2nd-rounders don't have guaranteed contracts like first-rounders.) In our wild fantasies that involve us trading multiple draft picks and JO's contract for a star, that second-round pick shouldn't be overlooked.