I have been getting numerous offline IM's from objects like these:
You have a message from #4 waiting for you in Second Life. Log in to see it.
You have a message from #24 waiting for you in Second Life. Log in to see it.
You have a message from #23 waiting for you in Second Life. Log in to see it.
You have a message from #8 waiting for you in Second Life. Log in to see it.
Not to mention annoying IM's sent by "SL Telemarketers" who seem to have a database of Avatar Keys and send mass junk advertisements on a regular basis.
When an abject (not an Avatar) sends an Instant Message to someone, it should disclose who owns the object and where it is located:
You have a message from Object (NewParis 122,122,23 Owned by MadamG Zagato) waiting for you in Second Life. Log in to see it.
At least you will be able to abuse report spammers and those who dutifully misuse Avatar Keys.