Be aware that LendingTree and Lower My Bills are not mortgage companies. They are lead vendors. You submit your application information and they sell it to lenders who compete for your business. I know because I've been buying LendingTree leads for years.
Now what happens once a lender calls you is entirely a different thing. Like some of the other posters suggested, not all lenders have the same integrity or morals. I hate it when I quote someone an interest rate commensurate with their credit, income, etc., and they tell me XYZ Mortgage quoted 1-2% lower! What that tells me is that XYZ is doing the bait-and-switch, but I have no way of convincing the borrower. If I was in the borrower's shoes I would probably go with the lower offer also. But what most borrowers don't know is that interest rates are pretty much the same everywhere, and your credit/income will determine what your interest rate is, for the most part.
Sorry, got off on a little rant there, but I think it's important information. My advice--call a few mortgage lenders in your area, get some referrals from friends/family, and go with the one who gives you the best, most knowledgeable, and most complete answers.