OK, thanks for the reply.
I don't plan on ever buying an unusual so I guess I'm safe for the time.
Tough, it seems (kinda) unfair because I would be left guilty because somebody doesn't do his homework on price-checks. Anyways, I don't think a person with a Unusual would not know about his/her hat's average price.
You can lock this discussion or something whatever is possible here if you want.

Backpack viewing sites are stupid if you ask me. You can view your backpack live from the Steam Inventory. Here's a link to your backpack which will always work for you: https://steamhost.cn/steamcommunity_com/profiles/76561198038592931/inventory/

So unfair trades aren't scams?

So there have been a few situations for me that seemed normal, but turned out that I was a "scammer" all along. Here are the situations:
1. I was in a trade server, saying in chat that I'm buying a Name Tag. Some guy asked me to trade. I accepted. He added Name Tag. I asked him what he wanted. He replied "i dunno maybe a rec or something". I accepted a trade, it seemed fair enough to me. So we made the trade. Then the chat and the microphones came all shouting and laughing how I scammed someone because Name Tag is worth 1.33-1.66 (Source: http://backpack.tf/pricelist/full as of 2013-01-21). The guy seemed not to mind it and leaved the server after about 10-20 minutes.
2. A guy was selling Strange Shotgun. I traded him. He said for me to offer. I gave him a Key. He was OK. We made a trade. Turns out I "scammed" another person because the Strange Shotgun is worth 4-4.33 (Source: http://backpack.tf/pricelist/full as of 2013-01-21). Then the I traded started to called me a scammer, judged about my sexuality and said he was having pee-pee friction pleasure with my mother. I then left the server of his annoyance.
3. Some guy was selling a key for 3 Refined. Ofcourse, I bought the key and the rants started how I was a scammer, because a Key is worth 3.33-3.55 (Source: http://backpack.tf/pricelist/full as of 2013-01-21) and that I will be reported to SteamRep, tough the person I traded really did not care as far as I can tell.

My question is, are any of these situations "scammy"?
Another question is, are bargain trades. (e.g. bought a key for 2.66 Refined) called scamms?

Thanks.