Some companies who stack use the approach of total gross funding. I.E. merchant ABC (in their eyes) qualifies for a max of $50,000. Funding Company Y only gave them $20,000, so there is room to add $30,000.

Now the folks out there who simply add for the sake of adding and pocketing quick cash, that's another issue entirely. One, alas, that will only be reigned in with litigation. Every funder should put a clause in their contract about what causes breach and what doesn't. However, there is inherently nothing illegal amount a merchant looking for more money. Simply because funder X's parameters aren't met, doesn't mean funder Y's aren't. The question arises "does the second deal impede upon the first deal?" If the second debit causes collection issues on the first, well, then you have a problem.