The fan is rated for the unit. I haven't heard of any recalls going on for that particular unit due to cooling or fan issues.
You CAN blow air into the heatsink channels, but ONLY do it in short bursts (very quick, no more than a second) so that you don't spin the fan too fast and spin a bearing out, which would quickly ruin any cooling ability.
Netbooks will never run at temps you'll get from aftermarket heatsinks on desktop systems. Very few laptops run below 40C under full load, and as I said, they're engineered to withstand that level of heat, I wouldn't worry about it.