Actually there are a few things to consider. Most people aren't using g-mail as the e-mail account that is on the BES. The way it generally works is you have your work e-mail i.e.
and your personal address
. The Microsoft e-mail address is managed by the BES and the g-mail is managed by the BIS. You cannot have multiple e-mail accounts on a single device being run by the BES. Most people don't realize that the BES is only managing the work e-mail address. Some people do forward their personal e-mail to the work e-mail account in a workaround to this issue of course.