Theorhetically there should be about as much correlation as a person's blood type and their temperament as a person. The blood type theory is pretty common in many Asian countries, to the point where that information is in the bio for important people. It's the same type of unrelated association that brought that theory into being.
You will probably see a higher incidence of IE/Bing usage among .NET developers, particularly if they've gone through any type of training. Microsoft is very good at promoting its own products through every channel it can. I used to believe there was an inverse proportion to a programmer's quality and the number of certificates they had, but I met a few certified Sun, Microsoft, etc. developers who were really good. It's luck of the draw there.
There may be some psychological effects going on here as well. People who are content with the status quo will accept anything that is set before them the first time as normal. They will feel strange and out of place by attempting anything that is not the default behavior, which would explain people actively seeking out IE and Bing--consequently leading to your observation. It's this type of person that will not be a good programmer. They won't be able to think in ways that will improve long standing problems. The same type of person might instinctively reach for Apple Safari if they grew up on a Mac.
However, once you get outside the defaults, there are a miriad of reasons why people choose the browsers they do. For example, for day to day browsing I choose Google Chrome due to its good security record and its very fast response. However, for web development I choose Firefox because the dev plugins on that browser are most mature and helpful. I'll check in IE and Chrome to ensure I'm not missing anything (covering the three most common rendering systems [Chrome and Safari share the same rendering library]). These days, the story is getting better on both Chrome and IE 8 and up--but still not as good as Firefox.
I think the most useful course of action would be to ask the person why they chose the browser/search engine they did. If the answer is along the lines of "I've always used it" or "I don't know", there is a possibility that they might be the status quo kind of person. Further questions will weed that out. If they give you a reasonable explanation, it shows they are thinking about the choice.
Who knows, maybe there is some benefit to the IE/Bing combination we aren't aware of. I personally doubt it, but there just may be.