No you cannot power the Raspberry Pi using its USB ports. The micro usb is the only way to power the RPi, apart from some other hacks I've seen involving solder (read the update).
Although it's not completely impossible, but you'd have to modify the RPi quite a bit to get that right. Please have a look to the Model B Rev 2.0 schematics.
UPDATE: As commented you can power the RPi using the GPIO pins and the USB (called back powering). I'm including the links, but credit goes to the commenter's.
UPDATE 2: As other Stackoverflow posts state, the new Pi's can only be backpowered once they have booted. IE: You cannot backpower the pi and boot it, the polyfuse will trip while booting.