I know you can fry a USBtinyISP if you short an output and it draws too much current, better the USBtinyISP blows than your motherboard. I love the little USBtinyISP they are cheap and they work, too bad AVR Studio does not support them directly.
The ATMEL AVRISP Mk II is a great programmer too, I have two on my bench, but the cost is much more than the little USBtinyISP.
Just my 2 cents,
wade