The Internet has changed things a lot. In the past, some agents would monopolize certain neighborhoods (especially the better ones) and refuse to show homes that weren’t listed within their informal buddy network. There are less able to control showings since buyers can view them on the Net.
I’ve read SD Realtor’s post for a while now. He’s a full service broker but charges discount prices; and I believe he’s part of the new (rather then the old) paradigm of real estate. I would use someone like SD Realtor to make an offer on a house — full service at discount prices, why not?