Robert X. Cringley had an article about this last year. http://www.pbs.org/cringely/pulpit/pulpit20050210. html
Basically what he said was that venture capitalists raised a whole bunch of money that they didn't spend during the last boom. This money is raised from investors and is given to the VCs for a limited time. The VCs make money from the management fees they collect for dealing with this money, usually 1 or 2% of the total amount. But, if they don't invest, then the money AND the fees get sent back to the original investors.
The time limit on investment is usually about 10 years. So if we say that the boom started around '96, then some of these limits have already expired, and the rest of them will expire within the next 4 years.
Use it or lose it. And the VCs will definitely use it.