I think it fits every sized company. VMware has announced the VMware small to medium business foundation bundles, which will be available shortly. The price points on those are extremely attractive to SMB customers.
Virtualization brings huge benefits to companies of all sizes. In fact, for SMBs the impact can be very significant, allowing them to do so much more with less capital expense, which is pretty important for an SMB.
In traditional SMBs, for example, you won't find [disaster recovery being done] in a lot. Why? It's too expensive, so they end up taking the risk. Unfortunately, those companies are the ones that never recover in the event of a real disaster. So virtualization makes it so much easier for a company to protect itself from a disaster. Companies of all sizes can certainly benefit from virtualization, and SMBs can show the value of virtualization to themselves a lot of times much quicker than large companies.