Yeah I'm aware of that and I see where you're coming from but it's obvious that people still find their way to Yahoo and Google anyways. There cannot be that many people that use MSN search just because it's the default.
There are that many people using Windows, because it is there by default... You'd be surprised. Don't forget about all the AOL'ers out there that still use AOL, thinking it is the only thing... And the Web TV'ers.. OH yeah, even they still exist. If I look at my stats for various sites I see search engines even as obscure as ASK showing up with great frequency. I think many give Google way too much credit. Sure I probably use them more than any other search. But when I cannot find what I am looking for, or am sick of the BH shit sites and wiki showing up on the first 10 results of a search, I use Yahoo, or Dogpile.
I completely agree with you that people will use the "default" choice because they don't know any better. My girlfriend once did a search with the comet toolbar because it had installed itself into her browser and it was there! Weird. It's funny that you also think people give Google too much credit. Many don't even know there are other search engines (which is scary). In a way, Google is many people's "default" search engine. But what I am saying is this: Say 95% of computers are pre-programmed with MSN search by default. Well only 10% of people use MSN search so the other 85% are switching to Yahoo or Google or some other search engine.