If you want details, you can read them here, but the lowdown is the Democrats are caving to give retroactive immunity for warrantless wiretaps to the Bush administration and the telecom companies.
As Mr. Greenwald notes, this is crap. OK - he doesn't say it like that, but I will. It's bullshit. I just called up my representative Kathy Castor, and she's against it, so she stays in my Good book. I also called the Obama campaign, so hopefully if enough people word will get to him and he'll speak out against it.