I would not be paranoid about log in usage...
The PW is only for the local LAN side connection. Only does this come in to play if you have the Remote Access enabled, then one would still need the PW.
New potential security risk: Now that I have my new DIR-645, H/W Ver.: A1 (originally F/W Ver.: v1.01), successfully upgraded to F/W Ver.: 1.03 and (almost) completely configured to my liking, I noticed another behavior apropos of the above discussion. The on-board Web-administration pages are accessible (with the required password of course) to **wireless** connections, in addition to the expected wired LAN connections. Unless I'm missing something (?), there is no way to turn off this wireless configuration access.
This seems unusual and potentially risky, since one cannot **physically** control who connects to the device wirelessly. For those who don't bother to set strong administrative passwords, strong wireless passwords, and/or other recommended security measures, their routers are vulnerable to drive-by attacks -- not a great design feature!
On the subject of passwords and user accounts, I also noticed that there is no longer a "USER" account and password available in F/W 1.03 -- probably just as well but something else tech support didn't seem to know.
This is a bit off topic, but F/W 1.03 also does not respond to outside requests on any ports that I've tried, to the extent that "stealth" has any real benefits. See, for example, the following results from "http://www.t1shopper.com/tools/port-scan/":
"68.34.86.240 isn't responding on port 21 (ftp).
68.34.86.240 isn't responding on port 23 (telnet).
68.34.86.240 isn't responding on port 25 (smtp).
68.34.86.240 isn't responding on port 80 (http).
68.34.86.240 isn't responding on port 110 (pop3).
68.34.86.240 isn't responding on port 139 (netbios-ssn).
68.34.86.240 isn't responding on port 445 (microsoft-ds).
68.34.86.240 isn't responding on port 1433 (ms-sql-s).
68.34.86.240 isn't responding on port 1521 (ncube-lm).
68.34.86.240 isn't responding on port 1723 (pptp).
68.34.86.240 isn't responding on port 3306 (mysql).
68.34.86.240 isn't responding on port 3389 (ms-wbt-server).
68.34.86.240 isn't responding on port 5900 ().
68.34.86.240 isn't responding on port 8080 (webcache)."
Best Regards -- jclarkw