It's accepted wisdom that only 150 of each last name are allocated, and that name is not reused. Well, conventional wisdom is a little out of date here - the names may not be being reused, but they're being rotated manually, and with (apparently) an approximate target of a thousand or so.

Highly popular names include Xi, Gray, Wind, Corleone, Ball, Starr, Goodliffe, and Market. This pales a little next to last names that were pounced on en masse, such as Epin (5700 or so) and Delcon (around 5400).

This makes a sense, as Second Life grows so rapidly. Even if there's no shortage of last names to use, the manual process used to switch them around means that more of some names will be grabbed quickly when something appealing comes around. I suppose that means if you want one of the popular first names, you're going to have to work a little harder to find a lesser used last name to go with it, or select something a little more exotic.