Not sure there is a limit. One is not published. The data size is very tiny, so you probably can store as many as you make; up to the limit of your i-'device'.
I will inquiry. In the meantime, if you run out of room, let us know...

I have about 22 stored in the app so far, and found that you can resize the voice icons by 'pinching' them. I was going to suggest that in the next iteration of the reface, you could add an SD card slot so that patches could be stored to the card. I think that would also up the interest in the product. Can't wait for SoundMondo.com to come online. I have patches I want to share as well as looking for ones I don't have.

Also I WOULD LIKE TO SUGGEST YOU ADD ROTATION TO THE IPAD APP, it is a pain trying to do everything in PORTRAIT mode on an iPad!!

Thanks!