Joba Chamberlain is on the active roster now, but will be used only as a reliever for the rest of the season. That way, he can be used "a lot more regularly," according to Joe Girardi.
While I don't have a problem with this temporary move, I fear it will re-open the debate of whether Joba should be a starter or reliever long term. If it turns out his arm can't handle a starter's workload, then moving him to the pen would be an unfortunate necessity - but that hasn't been proven yet, not by a long shot. He has to be given at least another full year of starting to see how he holds up.
An additional item of intrigue is that Joba may be sent to the Arizona Fall League to get his innings count up. The requirements for the league state that a player may not have more than one year of ML service time (before August 31st). As of Sunday's deadline, Joba had exactly 365 days of service time: he was activated August 7th, 2007, and went on the DL on August 6th of this year. Therefore, he's eligible for the AFL, where (presumably) he and Phil Hughes will stretch out their arm so as to increase their limits for 2009.