There could be any number of things going on here, not all mutually exclusive:
1) The military could finally be getting A-list intel and nabbing real insurgents by the boatloads.
2) Lots of innocent (or close to it) civilians are being picked up in sweeps. (Remember last year when the military acknowleged that the Red Cross seemed to be on the mark when it charged that 70-90 percent of prisoners were innocent?)
3) The election-timed suspension of the release of detainees is still in effect.
Again, I don't know which of these three factors or mix of them represents what's going on. But I'm not the only one who's skeptical that the military is suddenly awash in first-rate tips. As the top U.S. ground commander put it in eight weeks ago, "After the transfer of sovereignty, I anticipated more intelligence from the Iraqis. That increase in intelligence has not developed as fast as I would have liked."
Indeed, it's still difficult to figure out whether intelligence against the insurgency has actually increased. Back in December, it was still dismal. On the other hand, a Los Angeles Times article from a few days back suggests that things have improved of late: "commanders say new Iraqi army and police units have improved intelligence-gathering through their knowledge of neighborhoods and local political currents.".
Still, the Times article also notes, "[Army Brig. Gen. James] Huggins said intelligence analysts were sifting through information provided by U.S. and Iraqi officers and tips from Iraqi civilians to better understand Zarqawi's network of cells." So figuring out who's who, and where to look, and who to nab could take a long while, and it's not obvious that the recent influx of intelligence means the U.S. has suddenly become smarter at capturing insurgents. Which, of course, means that many of those current prisoners could well be innocent Iraqis. The practical problem here (along with the assortment of moral problems) is that eventually these innocent folks will all have to be released, and when they do, it's hard to think they'll still support the new Iraqi government. Interestingly, the Times article notes that the U.S. is no longer focusing on winning "hearts and minds" but simply trying to build broader public faith in Iraqi institutions. That seems like the sensible step at this point, but it seems difficult to build any such faith so long as the corrections system remains arbitrary and the jails overcrowded.