On the issue of when Obama deserves to receive blame or praise for the current state of the economy, it seems to me that any new U.S. President deserves a year or two to get his or her own policies in place before being blamed or praised.
This is just common sense to me. Obama is inheriting a huge mess in both foreign and domestic issues, and he will need time to put his own stamp on them. This isn't being partisan, just realistic. Likewise, if he had inherited a wonderful economy and a world at peace, he wouldn't be eligible for praise for awhile, because it would have been Bush's legacy.
I think this is true of any organization. When I come into a new church as pastor, I inherit a situation from the previous pastoral leadership that is either good or bad. It will take a good year or two before my own efforts result in either good or bad results. In the meantime, I deserve the benefit of the doubt, and none of the blame or praise for what I inherited.
So Obama deserves the benefit of the doubt through 2009 and even 2010, after which time, evaluation will be fairly applied to his efforts. In the meantime, any attempt to label this the 'Obama recession' or the 'Obama bear market' is just nonsense.