The problem with a limit is what limit to choose. 5bm is nowhere nearly enough. I have at least 3 projects that ive worked on that were far in excess of that limit. I use irc to send betas to folks to test it for me.
Personally (and this is just my opinion) I dont see where its the responsibility of mIRC to take on the "warez" pirates of the world. Also i dont see why others should be denied an option or feature because someone may use it improperly.