In the latest patent application from RIM, it looks like they may be heading towards some sort of advertising in emails. Their submission to the patent office, "system and method for incorporating multimedia content into a message handeld by a mobile device", essentially allows for the device to match keywords and phrases in messages to bring you ads. As the application states:
This (advertising) may be done by examining content in the message handled by a mobile device and matching portions of the message with predetermined criteria such as keywords or phrases. Upon finding matches, corresponding multimedia content is associated with a respective portion of the message content and access to the multimedia content is enabled through selection of a linking mechanism that is visually identifiable with the respective portion of the message. The message is modified to include such linking mechanisms such that upon viewing the modified message, a user may reveal the multimedia content by selecting the linking mechanism. It has also been recognized that multiple layers of multimedia content can be provided such that different types of user interaction can reveal different forms of multimedia content.
RIM has also filed for a patent that will allow them to see if any devs are trying to circumvent the new email ads. Now don't go crazy - there is no word of if/when any of this will be implemented. RIM applies for hundreds of patents whose applications never see the light of day, so we really don't need to worry (just yet anyway). If you're up to it, give it a read and sound off in the comments with your thoughts.