I haven't tried, so there might be some details I'm not taking into account, but it should be possible. There's nothing about the beaglebone hardware that I can think of that would prevent you from doing it; it's essentially a small UNIX computer with a robotics cape attached, so if there is a limit to the number of cameras you can use, it would more likely be at the operating system level.
There is only one USB port, so you would need a hub to connect more than one over USB. There are also some camera modules that can interface using the I2C bus, so that's another option.
I would do some google searching to see what people have done to use multiple cameras on a Raspberry Pi, as the project community is a bit bigger for that platform and I would expect any OS limitations to affect that as well. Someone may have already written up their experiences.
Just some random thoughts, I hope that's helpful.
-Jeff