My problem with this type of thinking is that is too easy for Y to swoop in and take over X for you. They have the team, reputation, and recent success. You, most likely, have nothing. Examples: "We are facebook for bicycles!": that's just a facebook group. "We are Heroku for PHP/Clojure/Python": http://blog.heroku.com/archives/2011/8/3/polyglot_platform/ These are my best examples, but if X is just a feature that Y…
Very true. This could be the case whether or not you publicly call yourself "The X of Y." I've always though that most companies fall in that category, even if they don't know or outwardly admit it.
So basically, we're all in danger no matter what.