It is becoming more and more often that an offer will come in (Low-Ball of course) on a property listing from an investor that has not even seen the house. I am obligated to present every offer that comes in for my sellers, and I do, but the offer must be explained delicately and in great detail to these home owners.
The sellers need to understand and not blame these investors (or the agents) for trying to get a good deal, after all, isn't everyone? It's just difficult for a seller to understand why someone is putting in an offer without seeing their home. This is their home, not just a property to them, and it's really hard for a seller to detach themselves from it and look at it as a business deal.
I would never discourage these investors from searching out the best deals on the market. After all, I often work with investors myself that have done the exact same thing. It is not their intention to insult the seller in any way, they are merely looking at the house as an "investment."
Sellers, the offer, even if it is a low-ball offer, is encouraging. Investors consider your home in an area that will produce "income" for them (either with or without some work to the house). They are considering your house as an investment, so that is a good sign that the market that you are in is one in which an investor is predicting that they will come out ahead. So, be happy to receive any offer. It will help you to understand your market better, and it will also help you to understand that your home/area really has value and is predicted to continue to hold it's value.
It can be heart breaking but it's the nature of this market.