You may not have noticed, but over the last few years, web and application designers rounded your corners. Buttons and app icons lost hard edges, and it seemed fine and refined. Everything started to look like this:
Design crazes certainly do come and go, but be on the lookout for this one. One subtext is that it may become a bit of an Apple-Microsoft battle. The iPhone has round cornered icons; the new Windows 7 operating system has gone square.
This move from clean lines to rounded ones and back again reminds me of when beveling your text was all the rage in the mid-90s. The faux-3D effect was sort of the faux-marble countertop of the web world, especially if you dropped a shadow on it.