Instapaper brings beautifully simple bookmarking to the iPhone

Earlier this week I was thinking about what type of iPhone app I could write to solve one of my own problems and this is basically it. Instapaper will make my commute (subway = no internet connection) much more bearable.

Did I miss something or is the registration system not at all secure? You don't set a password when you register and then you can sign in just by entering your username - or anyone else's that hasn't set a password. What is stopping someone from trying a bunch of email addresses or their friends' favorite usernames?

I understand that might be a user experience decision (especially when someone is on an iPhone), but I wouldn't mind a warning to the effect of 'hey - if you don't set a password, anyone can sign into your account by simply guessing your username'.

Great job by Marco of Tumblr