The moon is actually a very bad place for a telescope. Especially a large one.
Even though there is very little atmosphere, there is a huge day-night temperature variation: +100 Celsius in the day, as low as -173 Celsius at night.
The materials of the telescope have different thermal expansion rates, and this kills the precision of the telescope.
In the right orbit, a space-based telescope can be in constant sunlight, and the satellite designers can shade whatever parts they want to get any temperature they want.
Plus, it takes much more rocket energy to land something on the surface of the moon than to put it into orbit.
A very real issue is that launching a 100 meter primary mirror, even in pieces is well beyond our current capabilities.
Modern adaptive optics can take out a lot of atmospheric distortion.
I would agree that the best environment for a telescope is to keep it in constant sunlight, but how does the HST handle going through the Earth’s shadow orbit after orbit and still get very crisp photos? It’s orbit is only about 350 miles above the Earth.
The 30m/100 foot primary mirror is divide up into 492 hexagonally-shaped pieces that are each 1.4m (4.6 feet) across. The fairings on an Atlas 5 are four and five meters in diameter which is more than large enough to carry such mirrors.
http://en.wikipedia.org/wiki/Thirty_Meter_Telescope