There's a number of major memory usage bugs that have been fixed in Firefox 7 -- both leaks and issues with garbage collection and fragmentation. For example:

There's a number of major memory usage bugs that have been fixed in Firefox 7 -- both leaks and issues with garbage collection and fragmentation. For example: https://bugzilla.mozilla.org/show_bug.cgi?id=666058#c31 https://bugzilla.mozilla.org/show_bug.cgi?id=666058#c31 https://bugzilla.mozilla.org/show_bug.cgi?id=656120#c44 https://bugzilla.mozilla.org/show_bug.cgi?id=656120#c44 The second bug specifically should help resolve the "Firefox has been open for two days and now it eats my entire system" problem.