I can't say I know how fast the web is growing. I do have some idea of how fast Yahoo! and Google's search indicies are growing, and they aren't that exponential curve.

It's never going to be the case that the PARC algorithm we use will be as fast as Google's algorithm. There is simply a lot more work to do, so they stay a fixed width apart.

But the way that the industry looks at computing resources has changed a lot since when Google is founded. They're becoming a commodity to the point where you can rent CPUs on a hourly basis. Also, there are new kinds of hardware that are starting to be tapped (for example, over the last few years graphics cards have become more and more a platform for general parallelized computation) that make the task seem feasible.