Yeah, no problem. IIRC the RPi won't go to the max USB connections as per USB spec (256?), but you can connect many. I'm sure you are aware that some models only support 150mA on the USB ports. The official USB spec is for the USB unit to wait for a 5V signal from the host, which then draws some power as well. It depends how your miner or hub implements that (or not). In my experience it works better using a powered hub, even it the miner is "powered".
Yes I totally agree. Never plug miner devices directly to an RPI usb port, use ALWAYS a powered usb hub for better results.
