The "auto tweet" on the front page is a source of occasional consternation.
There are two specific behaviours that I've tweaked & improved.
1. If you had a problem with Twitter when authenticating, it would default back to tweeting (even if you'd previously deselected the checkbox).
2. People occasionally request a report (with the checkbox ticked, ie - send out a tweet), then a minute or two later seem to change their mind & request another report, with the checkbox unticked (no tweet). I guess they decide to read "Tell your followers" after they've clicked it?
Anyway, I've tweaked both these issues. The option should remember your choice - a bit hard to test, since I can't exactly call up Twitter & ask them to break so I can test things, but it should be good. Plus, if you accidentally select the wrong option, as long as you're quick about it, you should be able to overwrite your previous request by requesting one again - toot suite though!