Comment by hinkley

I've worked at a couple consultancies who played themselves by investing too heavily in one or two customers.

Once a single customer is 1/3 of your revenue they can start extracting considerations from you that may not be what your employees thought they signed up for. It's a good way to end up being a body shop. I don't have a philosophical problem with body shops per se, it's just that I don't want to work for one, so I pick places that should know better, but sometimes don't.

It can also be problematic if 2 customers account for 45% of your revenue and they both get the same idea, which can happen particularly when the market shifts. You have no way to call their bluff and move enough people to other projects to make it stick.