I am a region finalist & happen to know a few ICPC world finalists, and though one of them is very sharp analytically, I am not sure how good a proxy such problems are for a web developer, or even for most technical positions. Some of the best problem solvers I know CS-wise (not algorithmic puzzle solving, but real CS research/ implementation) are not that fast of thinkers to do very well in such circumstances without a lot of pattern matching through practice.