People didn't think Google was going to keep the same revenues for very long, so it was cheap for a couple of months after IPO. Then their profits started to be

People didn't think Google was going to keep the same revenues for very long, so it was cheap for a couple of months after IPO. Then their profits started to become eBay-like, and the share price shot up. They also brought out tons of products ('beta', etc) and that also buoyed up the share price. But the current share price depends on them continuing to grow, otherwise it could very well plummet.