First, we will never disclose your address to anyone else without first explicitly asking you if it's okay for them, (e.g. a Genome Canada review panel for our software development grant), to mail you. We hate spam too.
The applet version of Bluejay cannot store any data on your disk due to privacy constraints. To maintain your document cache, and store preferences from session to session we require a login to the database on our server. An e-mail address is the most convenient login name to use, because it allows us to notify you of rare asynchronous actions related to your Bluejay browsing. Example are the cache expiry of documents you've modified but not saved, or e-mail delivery of search results.