To be fair, the rating agencies are waiting until the market has determined bond prices, before committing to their new and improved bond ratings.
How do you know I am not. There will come a time when junks are worth picking up. (properly hedged of course)
The other half is that several banks don't know how much debt they have from those innovations as a result of the subprime meltdown. Maybe Krugman is calling for a more thorough understanding of these tools before widespread use?