move as appropriate:

Warning, there is a person going arround on STEAM adding you to his friendlist CLAIMING to be a bot working for valve. It is a scam, and I suspect he might try to do it to you.

Note* that valve WILL NEVER EVER ask you for any information using the steam friends system. It says that on their website. Any attempts are to hijack your account. Keep in mind that the name may change, but here is a sample of what you might see after accepting the friend invitation:

*sorry in advance for the language

Automated Verifiy: Hello, Steam Automated Support has detected multiple ip usage on this steam account. This account is in danger of being shut down unless immediate actions are taken.For verification and full control over this account please state your Account Name/Password. Thank you, and for any questions please refer to steampowered.com
Automated Verifiy: Please Note: Not Verifying Account Information, Your Account will be shut down within 24 Hours.
Automated Verifiy: Please format the information as : Username/Password
Green_Mon-key: omg i should resolve this as soon as possible
Automated Verifiy: Please format the information as : Username/Password
Green_Mon-key: If-youWant_This/Go****YourSelF
Green_Mon-key: You *** **** mother ******* idiot. You think i am that stupid dont you?
Green_Mon-key: why dont you go steal from the police department.
Green_Mon-key: like the ******* idiot you are
Automated Verifiy: maybe u want to know my breast size
Green_Mon-key: ooh can i?
Green_Mon-key: that sounds hott
Automated Verifiy: too big to be true
Green_Mon-key: you get alot of people with this?
Automated Verifiy: yep (^_^)
Green_Mon-key: one one hand, darwinism
Automated Verifiy: (O_O)
Green_Mon-key: on the other, you should be banned from the internet
Automated Verifiy: (>_<)
Automated Verifiy is now Offline.

P.S. if there a place you can report this name to steam?
Aslo, keep in mind that his steam friends picture is the steam logo. What ever you do, neevr give out your username and password.
No, unless you have their actual account name, steamID, along with IP and/or Logs.... there's nothing they can do but warn people about it. If enough people complain about it they'll have a spyder run through the system and look for anyone using that phrase, I guess...
I just came on the forums specifically to post this exact same warning.

Except I didn't have any comical chat logs, I didn't even add him.
i dont even HAVE steam friends! lol thanks for the warning green. ur chat was actually funny. but dont do that again only to protect the sake of ur acct.
Ya, If they were to warn you, they wouldnt do it with friend chat, and they already know how to get access to your account, they're steam, they know all :p ......Ill make sure to look out for that, and in the process, Ill make sure to have a little fun with him :D
yes i havent played in 2 days and i had a friend request this morning on my computer desk top from this guy
remember to not hit anything but the x to get rid of message or you may be hacked
deny any friends request unless it is someone in game your playin with that you trust or someone you know. If the name is unfamiliar that is sending a friends request while playin type in "who sent me a friends request" otherwise you should always deny ones you dont know