I only noticed this a day or so ago: the memory usage creeping up after only a few hours of having booted and doing little more than running Exaile (on Xubuntu 10.4).
Initially Exaile was just dragging and losing responsiveness (same story with GnomeMPlayer), now it reaches a point where it can play part of a song then abruptly crash as the memory usage runs up to 500+MB.

The process list reported that notify-osd had reached 578 MB, which is way out of order. In fact the the only way I can stop this happening has been to disable notification in Exaile/GnomeMPlayer on song changes. Even simple one-time notifications, like net connection, knock the process up by 2 megs where it remains each time accumulatively.

I noticed this is an officially reported Ubuntu bug since 2009 (ongoing to now). But I haven't experienced any problems before now.

Anyone got anything enlightening to say on this?

In most cases just waiting for a new version, or downgrading to an older version, for example by using aptitude can make a temporarily workout. This problem also existed when KDE 4 came out and the entire nepomuk service could consume all memory being in the machine. A few versions later, this was solved.