On my 3G, all of the emails list as coming from me obviously
I have all my accounts forwarded to mobileme and this is not what I experience. Are you forwarding as a "rule" in outlook or do you have it set up at the server to forward your mail. No matter what account is forwarded to mobileme...it shows up as being sent from the original sender.
Set it up at the server to forward to mobileme and have it delete the copy from the server.