For Kyoto:

Translated: the developed countries realize they aren’t going to be able to meet their Phase I commitments without fudging the issue, while the developing countries, currently commitment-free, want them to cut emissions deeply but do not want commit to any cuts themselves.

Actually the first few years of Kyoto will be very easy. The European price dropped to five Euros per ton before they opened up the rights to be used in Phase II.

I suspect some of the collapse in value of the carbon credits is due to sale of bogus credits from former eastern block countries, among other places. Under Kyoto, as I understand it, the buyer is not responsible for the validity of the claimed credits, and the only penalty for the seller is to be faced with stricter limits in Phase II (assuming they even sign up for it, which they probably wouldn't if they had signed onto Phase I only for the scam.)

There's also Canada pulling out of the carbon market. The only way they were going to comply was by buying credits, but with the new government they've decided that's not worth it.