the old code stored the whole bookmark as a single string so storing a few of them in ram is no problem. A bookmark now is made up of the playlist_control file (which can be BIG) as well as resume points and the filename of the actual .bmark file.
At the very least we store the filename of the .bmark. This means unique will only work if you actually start playback from the bmark, or you keep adding after the first one was created (this may be the way its supposed to work?)
The next option is storing track title and resume points as well. (hmm, and on that point I should change it to show some track info instead of the filename in the bmark viewer...)