The semantic text mining Alchemy API is now a member of the API Billionaires Club. The service, which makes sense of raw unstructured data, averages 65-75 million requests per day, according to Alchemy's Elliot Turner. That brings the monthly count above 2 billion API requests.
Additional third party integration with Gmail has been possible (you only have to look at all the contact import features from sites like Facebook), but these have either been clunky manual procedures that involve exporting contacts to a CVS file, or they require you to supply your email password. Neither option is all that attractive. Now there is an alternative. Google have recently added the ability to access the IMAP/SMTP features of particular Gmail account using OAuth.