When registering a DCS account from within DCS, almost anything can be entered into the password field.
When one tries to login, if the password does not follow the security rules, that password is simply not accepted. DCS reports that the password entered is wrong.
DCS needs to follow the same password rules as the website.
It was only out of random frustrated attempts and trying "anything" that led me to try to register on the site even though I had already done so in-game.
Speaking of which, the password security rules are really irritating. DCS is a low-volume flight sim. There is no reason to require a capital letter and a number. The risk of account break-in is low (oh no, someone can fly with my account!), and the security increase is marginal at best.
For a humorous take on bad password rules, see this XKCD comic:
http://xkcd.com/936/