Some problems you
want to have. A huge firm signing up is definitely a problem you want to have.
I was first introduced to this concept by a colleague who was going to serve customers manually instead of us programmers automating it. I said he was going to have a major issue when lots of people sign up. He replied "That is definitely a problem I want to have, I hope I get completely overloaded, because then we have the money to automate it".
I guess it is related to Paul Grahams "do things that don't scale", but "problem I want to have" is broader.
Since then I always evaluate if certain problems are the ones I want to have, because then I know I can postpone them.