(and if Microsoft had any sense, they shouldn't have allowed it to). =P
Ah, but the very reason they allowed IE to load BMPs was because they had lots of sense. Maybe not moral sense, but definitely business sense. People are being encouraged to be lazy and upload BMPs without converting to JPG or PNG. Other browser users are left in the dust. What must they do to view the BMP files? Either download and view in an external program every time (big pain) or install IE once and never think about it again. The conspiracy theorist in me says that Microsoft is banking on this. Moreover, they didn't do this until they had enough market share that their position wouldn't be threatened by it.
They do this in other ways too. IE is extremely liberal about interpreting HTML. Tables don't need to be closed, entities such as < don't need the ending semicolon ( I see this all the time in Netscape; sticks out like a sore thumb), etc. Again, browsers that adhere strictly to the standard get left in the dust by lazy web "developers" who can't even be bothered to write proper HTML. Microsoft's entire site is unviewable in Netscape - I haven't analyzed it to tell whether this is Netscape's poor support of newer standards or improper HTML that chokes it up. Either way, though, this is surely intentional.
Well, enough paranoid conspiracy theories for today. Stay tuned for tomorrow's episode: Leveraging the Desktop OS Monopoly to Take Over Entirely New Markets!