This Fed cut does not address the issues causing the global sell-off:
-Illiquid Credit Default Swaps written against thin air.
-Insolvent Mortgage Insurance Companies
-Insolvent GSE's (Freddy Mac, Fannie Mae)
-Crooked and disfunctional bond rating agencies like Moody's, Fitch, and S&P.
The only thing that will fix this is if Buffett takes over Moody's, Buffett and Goldman absorb the mortgage insurance agencies, and the US infuses Fannie Mae and Freddy Mac with money.
The Credit Default Swaps are something nobody can fix. However, by stabilizing the institutions upon which they depend, they could be stabilized somewhat.
The Fed could cut to negative zero and it wouldn't make a difference.