Avatar Key

I have been asked a couple times how to use the AV key to find an avatar on the grid. Can someone tell me if this is possible, and if so, how?

If it is possible (which, to my knowledge, it isn't currently), it is a bug which allows privacy breach, and as such will be patched with a vengeance.
A while back there was a bug which allowed you to track an avatar to the new sim immediately after a teleport; that may be where the idea comes from.

Currently the only methods I'm aware of involve getting someone to respond to an IM or auto-deny corrupted inventory. If you're looking for a non-intrusive method, then no

Given the av's key, you can find out whether they're inworld or not, their name, their SL birth date, and whether they're payment info is on file and/or used -- the same info you'd get from looking in their profile.

I don't know what affect hiding online status has on this.

You can query the dataserver for people's online status, even if they hide it in their profile.

Just as an addendum to Day's comment: All inventory handling and IM (including group IMs) tag your location into the message sent to the client, so if you look at the data sent on protocol level, you can find people's location that way. -Forcing an autodeny is a sneaky way to force people to respond in *some* way to an inventory operation.

But even if it's technically possible (with a custom client or proxy), you'd still be in violation of the ToS for stalking.

"Certainly, I can help you there! This would involve having a robust and self-healing sensor grid across every sim; propagation across mainland continents would be fairly quick, though the associated social engineering and/or land purchase required for presence in private islands might be slightly slower to achieve.

"Now, shall we talk about pricing, at, oh, L$20K an hour plus expenses? I would expect half of the estimate in advance."

Just to clear things up for the OP, Yes it is possible and easy to do if you know how to script. As for the how - I have to ask why do you want know about it? The privacy setting is there for a reason - if people do not want you to know they are online then you should respect that. if you have something in mind that is not invasion of privacy/stalking related then please share with us what it is

What the OP asked is NOT possible via script; they didn't ask to find out if someone is online (which is indeed easy via script), the asked how to find out where someone is on the grid. That's a whole different ball of wax.

Not quite true. It is easy to get the online status with a script (llRequestAgentData). But you cannot get the actual location of the avatar that way, which I think was what the original question was.
Getting the location is possible, but you need to run a special client or proxy to inspect the data traffic sent between the servers and the client, and even then you can only see it if they somehow respond to you. -Which, as Day pointed out, you can trick them into doing automatically by deliberately forging an incorrect message and injecting it into the data stream.
-Whether you consider that "easy" is up to your programming experience, but it is *not* done through LSL scripting.

OK I misread the OP statement to say this: -

I have been asked a couple times how to use the AV key to find *if*an avatar *is* on the grid. Can someone tell me if this is possible, and if so, how?

And by on the grid I took that to mean online. My mistake I simply misread slightly. I was not asserting that finding someone's location on the grid is easy via script - because as we all know it is not.

An external site stores names AND keys on the same domain as of early 2008 (and other detailed info like groups, picks and description text).
llHTTPrequest can load tata from it and anyone can make some key2name or namekey procedures that do not require that person to have been in the same region as you, like in other keyname procedures.

Some use of the data on that site CAN violate the SL TOS (havign access to data without agreement that you should not have otherwise), but most usage will not (because most data is acessable easily otherwise anyways).