Cameron Marlow, a researcher at Yahoo!, has put up a simple tool to calculate the number of key presses it takes to enter in data via multi-tap. His goal was to see how long different URLs would take to key into his mobile browser. Since predictive text doesn't work for non-words like most URLs, multi-tap is the most common option.
Marlow noted that ironically .mobi takes more key presses than .com, .net and .org. Of the most popular top level domains, .net is the shortest at 6 taps (.mobi is 11 taps!).
[via Waxy]