I don't think this Jason Kidd trade is a very smart move for Dallas. Kidd is still a better point guard than Harris, but at this point in their careers the margin doesn't justify giving up so much additional stuff in order to get him. In particular, when you swap Kidd for Harris you're getting better rebounding and defense in exchange for worse shooting. That's fair enough, but the other players Dallas is sending to the Garden State are going to cost them defense and rebounding. On top of that, trading young for old and giving away picks and expiring contracts in the process hurts your team's future.
Basically, like Phoenix, Dallas seems to be responding with panic to the Lakers' acquisition of Pau Gasol. But just because a conference rival improves doesn't mean that a trade that didn't make sense a month ago suddenly does make sense today. If Andrew Bynum returns healthy, then the Lakers will be a very difficult team to beat. There's nothing written into the fabric of the universe that guarantees there are any possible trades San Antonio or Dallas or Phoenix can make to become better than LA. Oftentimes, teams become very good because other teams agree to make stupid trades with them -- that's what happened with Boston, and that's what happened with LA. Teams in that situation can only hope that some other team wants to come along and make a one-sided desperation deal. But instead of waiting cautiously and hoping for a sweetheart deal, Phoenix and now Dallas are making panicky moves.
It seems to me, though, that the one thing you never want to do in the NBA personnel market is put yourself in a position where you feel like you "have" to do something. You "have" to move Kevin Garnett, so you accept cents on the dollar. You "have" to sign a big-ticket free agent so you give Larry Hughes a huge deal. You "have" to respond to recent big trades, so you give away draft picks and depth in exchange for a smallish upgrade at the point.
Matthew Yglesias is a former writer and editor at The Atlantic.