Prusa i2, why not have the motors on bottom?

I got around finishing my first low budget printer a couple of month ago, the Prusa i2 , and I was just wondering why aren't the z axis motors on the bottom instead of the top? Occasionally this gets pulled out and falls and it seems that it can completely be avoided by placing the motors on the bottom. This would also lower its weight from the top to the bottom and possibly make it more stable.

Answer to my own question here

It all comes down to if you are using lead screws or threaded rods, with threaded rods it proves to be an advantage. All explained in the article above for those curious

That article is a good find.
Very intetesting.

Im using 8mm x 1.25 stainless a2 threaded rod and nuts for my prusa i2 lead screws as i thought they may be better quality as they dont have to be treated to resist rust so no coating of zinc. They do feel smoother to the touch if you wind them through your fingrrs compared to zinc coated mild steal.
With a small dab of lithium grease the seem to do the job well.

Ive also got bearings in a holder at the bottom and metal couplers cut with a spiral to attach them to the motor shaft as i didnt trust the plastic printed coupling.
Like this:
[www.ebay.co.uk]
I dont think my lead screws are going to drop with that set up.

Gordon