i noticed that Firefox, unlike Chrome and Internet Explorer, doesn't run in the Low Mandatory Level (aka Protected Mode, Low Integrity)

Google Chrome:

Microsoft Internet Explorer:

Mozilla Firefox:

Following Microsoft's instructions, i can manually force Firefox into Low Integrity Mode by using:

icacls firefox.exe /setintegritylevel Low

But Firefox doesn't react well to not running with enough rights:

i like the security of knowing that my browser is running with less rights than i have. Is there a way to run Firefox into low rights mode? Is Mozilla planning on adding "protected mode" sometime? Has someone found a workaround to Firefox not handling low rights mode?

Update

From a July 2007 interview with Mike Schroepfer, VP of Engineering at the Mozilla Foundation:

...we also believe in defense in depth and are investigating protected mode along with many other techniques to improve security for future releases.

After a year and a half it doesn't seem like it is a priority.