Hey Web 2.0 sites! Do NOT make my profile page trickily unlinkable. In other words, do not:

1. ...make your front page act as my homepage. For example, if I want to share my calendaring info or event info with my friends, don't have me send them your URL only to find out that they can't see my info because they have to be logged in as me. Prime offenders: 30Boxes, Upcoming.
2. ...make my profile page act radically different when I'm logged in and when I'm logged out, even if it's not the front page. If you find yourself coding a "click here to see how your profile page looks to other people" link, you're doing something wrong. Prime offenders: Douban.
3. ...assign me a number so I can't guess my friend's profile page even though I know his username. Prime offenders: Upcoming, previously MySpace.

Please do: give me a profile page to share with my friends, make a clear distinction between my public profile page and my personal control panel (or make them similar enough so that being one and the same is no big deal), and make profile URLs guessable.