Posted this elsewhere too. A friend who's a huge cycling fan told me this was coming a few weeks ago. The feds dropped it not because they don't think lance doped, but because they can't prove he did to the level of proof they're required to do.
With USADA the standard of proof is different and basically they can present evidence or testimony and Lance almost has to prove it not true.
They apparently have quite a bit of evidence and testimony that says lance and 4-5 others were actively doping, telling others how to dope, and even apparently distributing doping materials to other riders.
He's apparently very likely to be charged with it and it's apparently the most danger he's ever been in with respect to drug charges because the burden of proof will be more on him.