It seems like there is a bit of confusion about MP3 capabilities on the BlackBerry 7130 and 8700 series devices. To make a long story short, you can play MP3 ringtones. You cannot, however, listen to MP3 files or stream MP3s to your BlackBerry. At least not yet anyway.
So, to be clear. If a BlackBerry sales rep at one of those kiosks near the food court in the mall tells you that the BlackBerry can play MP3 files, they either didn’t pay attention during that part of the training program, or, they are talking about BlackBerry ringtones and ringtones only.
You cannot play or stream MP3s on your BlackBerry.