Plus, the backpacks make you less of a target for thieves and muggers. Laptop briefcases and messenger bags tend to be targeted more often because of the likelihood that they carry what people think they carry... a laptop. If you use a backpack, that doesn't have logos or something that outwardly declare that it is, in fact, a laptop bag, then you minimize your chances of being robbed. Much like how thieves target people wearing white earbuds because the odds are that it's connected to an iPod and not something else.