...Sun was able to slash the number of printed copies of proxy materials for its 2007 annual shareholders meeting from 800,000 to 75,000. Printing nearly 100 million fewer pages translates to saving 11,964 carbon-absorbing trees, according to the Environmental Defense Paper Calculator. (from the Green Wombat blog)
Here's the thing. Forests that are cut down to make paper (as opposed to those cleared for agriculture) generally get replanted with new trees. A forest that's been cut down and replanted will fix lots of carbon as it regrows. But, a forest in equilibrium will not absorb much carbon! So perhaps using lots of paper and burying it in landfills is better, in terms of atmospheric CO2, than "saving" the trees.
(Now, I'm willing to bet that at the moment more CO2 is released in the process of harvesting the trees, making paper, transporting the paper around, etc. than is sequestered--- so reducing paper usage is still a net win on that grounds. But it's not because papermaking decreases the amount of carbon fixing that takes place in the forest.)