There are a lot of games that don't necessarily make the process of having an alt a smooth road, but almost none that outright prevent you from even indulging the idea. However, Freesky Online has come out with a recent developer diary that states precisely that: no alts allowed. And while their decisions outlined therein are focused highly on the idea that as a free-to-play game there need to be certain measures in place to prevent abuse of the system, they're applicable to many of the issues that players of larger MMOs have faced.
An obvious example is the longstanding practice of "bank alts", which is specifically referenced in the diary -- as far as the game's developers are concerned, it's abusing the mechanics of the game for unscrupulous means. There are certain games where it's considered standard practice to have at least one character just for banking purposes, but there's a point to be made that this is circumventing the hard-coded limitation of how much space a single character has to store items. The ramifications for other games are likely small at the moment -- it's unlikely that CCP is going to start deleting extra characters, for instance -- but the concepts are interesting to anyone who plays games where alts are frequent.