@HikingStick
Minnesota ftw!
First of all, thank you for the well thought out and written response. You are the kind of person I would LOVE to trade with. 
I completely understand and sympathize with where you are coming from. I thoroughly understand that life is more important than trading cards with random people online. I myself started trading here on Deckbox right after I got married, when I was working full-time and when I was still going to college full-time. I understand what it means to have to do some prioritization.
The thing is, the people I had opened trades with were not only logging on everyday, they were actively accepting and completing trades while mine was just sitting there being ignored. Also, I could see that they had looked at my trade, because the little "new message" flag had been cleared. It just amazes me that they can't even bother to type a quick sentence about what they're thinking. Even something as simple as "No thanks," or "I don't actually need that anymore. Thanks," or "Let me think about that for a little bit" or even just cancelling the trade is infinitely better than letting it sit there and not responding at all. Is it too much to ask for a tiny bit of communication?
Now I admit that sometimes I can get a little bit impatient, but should I really let a trade sit there for 3-4 days after it has been looked at it just waiting for them to respond?
About the status flag you mentioned, I think that would be a fantastic idea! Being an application programmer myself I can see how it shouldn't be all that difficult. Thought I'm sure, like you said, it would be a bit low on the priority list.