I like how Seth Godin states everything so clearly. Usually it's a pithy piece of advice about how to do the right thing, do right by your product, and thereby do right for the market by serving the right users with the product they want, and forgetting about trying to serve everyone else.
Here's one thought about really knowing your use case and putting it out front for the market to see, and letting it guide your conversation.
Many organizations will take any customer, any time, and bend and writhe to accomodate money in whatever form it arrives. Other, happier organizations understand the benefit of optimizing for a certain kind of interaction, and they have the guts to decline the part of the market that doesn't want to use their tool/organization the way it was intended.
And what to do if your use case becomes irrelevant (ouch!):
You'll often be wrong about what the market is and what it wants. When that happens, time to either shift your use case (and the way you're organized around it) or stick it out but be prepared for a long, tough slog.
Hear, hear. More over here.
http://sethgodin.typepad.com/seths_blog/2011/07/articulating-your-preferred-use-case.html