Carlos Boozer is not a particularly good defender. By points per possession allowed, Synergy had him ranked in the 54th percentile, and that number is probably aided by the fact that he plays for defensive mastermind Tom Thibodeau and is surrounded by a bunch of relentless ballhawks.
His contract—he's owed $47.1 million over the next three seasons—isn't one you would call desirable, either.
And he's battled injuries throughout his career, although he did play in all 66 games last year and his shaky reputation in this area is probably a little unfair.
But in a post-lockout NBA economy, some combination of these factors mean that he's almost certainly available for the right price. According to Marc Stein, that price might ultimately be the veteran's minimum after the Chicago Bulls decide to amnesty him after this season or the next.
It should never get to that point, in my opinion, because Carlos Boozer is still an effective NBA player, and there are plenty of teams that could use his services.