A small memory leak in zope.interface may sum up to blow up your RAM usage.
This got fixed.
It affects Zope 4.4.1 to 4.5.1 and Plone 5.2.2.
Any Python project using zope.interface 5.x is affected as well.
This is i.e. true for twisted (where Richard van der Hoff found the the problem). Check your dependencies for zope.interface and the version used.
The memory impact differs on the usage of zope.interfaces. It gets bigger if dynamic interface assignments are used often.
If you are using zope.interface 5.x it is recommended to update zope.interface to the 5.1.1 release.
Thanks to Richard, Jason and the others involved in fixing the bug in short time.
[updated: 2010-10-01 10:15 am ]