I often don't get responses from offers to buy sites/domains from the little guy
Yeah, same here.... I've inquired on quite a few domains/sites that were supposed to be for sale, and rarely have I ever received a response. How do these people expect to sell?
As for making offers on the bigger sites, I have occasionally had offers from people wanting to buy a copy of "the script" that I use on one of my sites. I like to respond by saying that my "script" requires 12 servers and a full-time network admin to operate, and it can be purchased for $500,000 cash. I rarely get a response from that either. Hmmmm, maybe the problem is something I said....