It Really Is Difficult To Find Sellers
The difficulty is in the number of people capable of selling. Many potential sellers are upside down (owe more on their home than the value of the home). This occurred due to the ease of lending and the increased values that led to the mortgage meltdown.
Now that we are seeing modest increases in home values the seller's are still upside down. They do not suffer from hardship cannot refi, maybe able to get loan modifications. But in most cases they are inbetween. That causes them difficulty in being able to move up or down and they have an asset with no value.
No matter what happens in the market they are stuck. As prices rise more and more get out of the condition. Pray for a hard up tic.