There are players adding you as friends as soon as you make a trade offer on the trade outpost site. They will send you a message that says add their friend on steam because they are getting error #503 and can not get in contact with you. Don't do this the link they provide is a fake website designed to look like a steam page if you attempt to log in they steal your info and account. Thankfully my fire wall caught the site as soon as it opened but beware. Thanks for taking the time to read this warning.