Naively (and correct me if I am wrong) but I think that a Pi with its 4 USB ports could handle 4 stick miners - subject to the following conditions:
Each stick would be attached to the pi by one of those USB cables that has an auxiliary power connector.
The auxiliary connectors would plug into a USB charger type device.
As an example I have a Vinsic USB power adapter that is specified as 40W and has 5 USB power outlets - so that a Pi and 4 sticks could be powered from the device.
http://www.amazon.com/Vinsic-5-Ports-Charger-Motorola-Cellphone/dp/B00L1XQBBMI quite like this device which I have used to power a couple of PIs and charge a phone and a battery at the same time.
Whether this is sensible of course is another matter.
This might work, if you can find the right kind of "3-connector USB Aux cable". My experience with the USB Aux cables was that they would 2 "A" ends for plugging into two sockets on the computer, and the 3rd was a mini-USB connector to plug into a portable hard drive. In this application, instead of the mini-USB, you would need a "Female A" socket, as if it was a USB extension cable. I haven't seen such a cable, but I haven't ever looked.
I would think for most folks that a powered USB Hub would be much simpler and less complicated with fewer cables involved.
As for the Hub that Phil mentioned above, I too found that despite it's 10 USB sockets, I could never get more than 6 to work consistently and reliably. It looked great in terms of socket spacing and such, and I was willing to supply more 12V than the original power brick, but It always choked when I tried to add a 7th stick. I ultimately just used it as a "widely spaced" 5 port hub where it worked just great. I was running U1, U2, and Red Fury stick miners at the time.