Usually USB hubs are not designed to power anything else from the USB devices such as pen drive or your keyboard and mouse. Those USB hubs generally can provide maximum 500mA current. However the Raspberry Pi normally draws 200-300mA but sometimes it can draw upto 750mA!
[Bharath] shows us a hack he did to allow his Raspberry Pi powered by USB hub, by combining the hub with a power supply. The maximum output current of the power supply is 3A, so that’s more than enough for this purposes. The The reason he started this project was because of the messy cables. Indeed after the modification the whole thing look more compact and no more messy cabling. However this project is only tested with the Raspberry Pi, so do it only on your own risk.
If you are not a DIY guy, there is also existing Raspberry Pi USB hub that can power your Pi. The PiHub is a 4-port USB 2.0 hub designed around the Raspberry Pi. 3000mA power supply, 4 downstream ports. Great for hard drives and power-hungry gadgets, including mobile phone charging. Also, It’s looks like a Raspberry! Kawaii!