I'm with Jago on this one,
there should be stacking of potions, at least 5 or 10 of them, 50 would be too much,
and not only for reasons Jago mentioned.
I have premium account and I really hate when I have to have full 2nd inventory of health potions and 3nd inventory full of mana potions to make through one dungeon which has 11 stages...
In my inventory I have different gears, rings and amulets, for different situations, and lots of resources which I need when I make items, and it takes up lot of space in inventory, if we had stacking of potions everything would be less anoying,
sry for my english I'm from Croatia:)