We will not sell your data. The only information gathered is the standard stuff from Google Analytics, which includes things like your location (gatehred from your ISP), and your browser/OS information.
We encrypt all feed/group data before putting it in the database. Nobody looking at the database can see any data in plaintext - not the group name, the source URLs, or the parsed feeds. We don't care about, nor want to know specifics about, the items you are interested in.
If you click to Delete Account through the account settings, we will remove all data created by you in the database.