When relying on a third party web services it is my experience that being transparent about who you are and how you are using the service makes the service providers much more cooperative. The most simple way to do this is to provide a descriptive useragent-string that includes contact info.
E.g. MyScraperBot/0.1 (+http://bertel.dk/humans.txt)
So when a bug in your code fires 10.000 requests/second to the service provider, they have a clear indication that your not a disrespectful scriptkiddie trying to their service offline for the lulz.
And and thus encourage them to reach out to you to help you fix the bug, instead of just banning your ip-range.