Ok, I'll bite.
There is quite a bit of antaganism between realtors and investors. Many times, they are in direct competition with each other. Preforeclosure investors don't want a realtor involved because another middleman just eats the profits. Further, a well advertised property will generally get a higher asking price. Whether that asking price is higher than the commisions charged is debatable.
Realtors also do not like dealing with investors because many just don't understand us or don't want to. The Realtor I worked with the last few years got looks of shock and awe when he told his collegues he went to a foreclosure auction with me. Not one other agent in the office had ever been to one and many thought it very strange of him to do so (even though, if I had bought, he would have got the listing within a month on the flip.) Also, at least personally, most realtors I run into just are not knowledgable about the field they represent. I cannot tell you how many times I've run into agents where I know their job better than they do. I had one agent actually tell me it was illegal for me to put an unrepresented offer in on the house he was representing. Ignorance of this level won't last through the current downturn though.
Also, many, many of the Realtors I've run into are not exactly, well, how to put it, honest. I watched one house go into foreclosure because a Realtor came in at the last second, disrupting an investor deal with a promise of a well above market sales price. Yep, he bought the lisiting. Amazingly enough the house, in its rough condition, didn't sell in time and the house was lost. Then there's the enternal, "We already have another offer, make a better one..." line. And amazingly enough when I decline to make said improved offer, the house is reoffered to me soon after at my price, or stays on the market because said offer didn't actually exist (or the other offer fell though, but then the listing status should have changed.)
And then there's the do anything to get a sale attitude. Offer a 4% buyer's commision on a nice house and watch the feeding frenzy begin as every represented buyer within 50 miles shows up to see the house. I understand that agents need to eat, but a system where the higher the price, the more I get paid isn't too fair to the buyers.
Anyways, this turned into a bit of a rant and that wasn't my intention. I am not anti-realtor. I've sold everyone of my houses through a realtor (eventually). A great realtor is an asset. Someone who knows what I do and is a better negotiator than I. Also, first and second time home buyers do need someone to help them through the steps and to help them make sure they aren't buying a ticking timebomb of a house. It takes a lot of time to pick up the skills needed to do this. Anyone can learn the paperwork in a month or so, but real value added takes time and experience.