OK, here's an arbitray example. You go to your local EMS with the best of intentions to learn about backpacks and see what they have. You're not looking for a specific pack, you just need to start somewhere to educate yourself. The salesperson urges you to try on several different packs. The Gregory Baltoro seems to fit your needs (sorry, bad example as it's very heavy), but you need to think about it before spending that much money on a backpack. Here's what your comparison shopping reveals:

EMS $289
REI $289
Backcountry.com $246
Campmor $240
MoonTrail $239
Base Gear $232
Oregon Mountain Community $230
Tahoe Mountain Sports $216.71
Campsaver $216.71
Sierra Trading Post $180 (2007 model?)

I guess the question is, to save $73 would I choose to buy from Campsaver, even if it means having "stolen" the time of the EMS salesperson? That $73 becomes very significant when multiplied by several pieces of equipment across several sports. In the past year I've bought major equipment for hiking, backpacking, skiing, and kayaking, and smaller items for all of those plus biking. I'm guessing that shopping for the best price has saved me between $500 and $1000 in the past year.

Is it the premise of some posters that getting information from a store creates an obligation to purchase? I think that getting information is only the first step of a potentintial purchase. An actual purchase depends on much more than information.