I appreciate that you'll want to limit users of the no-key API, however I fear that on a daily basis I might exceed the 300 limit in testing alone.
I certainly don't want to hammer the API, but my site isn't public yet (nor ready to be public) but I would like the ability to potentially reach 400 or 500 a day (works out to 1 or 2 every 5min)...
Register an API key for the application anyway. You can always go back and edit information later.
The main thing behind the API keys is that you should limit it to 1 per potential/realized application. It would be bad if you made a developer API key and suddenly all 10 of your apps are using the same key.
When they say that no-key is for testing, they mean people that are just playing around with the API and have no interest making an application yet. If you at all have any plans for an application, by all means make an API key. Even if you don't know all the info for the app, still register it and go back and change it later.
