Starting with iOS6 there will be the option to have multiple signatures based on your email account. I have a personal account and business. I do not want my personal email to have my business signature or vice versa. Starting with iOS6, I can have a different signature for each mail account. No more will you see the following attached to every email:
Sent from my iPhone
This ability has been available if you chose to jailbreak your iPhone - no longer. I cannot wait for iOS6.