As for "stalking"... a small hint: you can connect to any server with a slightly patched engine and stay "unconnected" (only appear in status, not in scoreboard or anything else usually visible) and read chat.
You do take up a player slot then, however...
OTOH, it's in the interest of the other players to recognize players.
Also note that there is no safe way to "identify" a player by an unique ID. The only way a server could do that would be storing the ID in a cvar on your client; this ID however will disappear when you delete your cfg file. There is no other place a server can store data on. So as a solution to play "anonymously", join the JustPlay clan which is there for this very purpose
http://ouns.wikispaces.com/clan.jp
However, adding an unique ID is planned, however in a way that different server admins see different variants of the ID (for example, the ID could be hashed together with the IP of the server you connected to, so the server can't find out your true ID, but just a string that only it will get).
1. Open Notepad
2. Paste: ÿþMSMSMS
3. Save
4. Open the file in Notepad again
You can vary the number of "MS", so you can clearly see it's MS which is causing it.