Michio Kaku wrote a fascinating article/warning for Salon hypothesizing that Moore's "Law" (or the computing "law" that says chips will basically double in effectiveness about every 18 months) will start to decline and will eventually become a relic. Here is the crux of his argument, but the whole article is worth reading:
Around 2020 or soon afterward, Moore's law will gradually cease to hold true and Silicon Valley may slowly turn into a rust belt unless a replacement technology is found. Transistors will be so small that quantum theory or atomic physics takes over and electrons leak out of the wires. For example, the thinnest layer inside your computer will be about five atoms across. At that point, according to the laws of physics, the quantum theory takes over. The Heisenberg uncertainty principle states that you cannot know both the position and velocity of any particle. This may sound counterintuitive, but at the atomic level you simply cannot know where the electron is, so it can never be confined precisely in an ultrathin wire or layer and it necessarily leaks out, causing the circuit to short-circuit. According to the laws of physics, eventually the Age of Silicon will come to a close, as we enter the Post-Silicon Era.