I can't count the number of people who come into my open houses and ask if the seller will take an offer substantially lower than the current asking price. It's great to be a buyer right now and they are all taking advantage of the current market...or trying to.
An increasing number of sellers including builders of speculation "spec" homes and frustrated homeowners and pulling their homes off the market. This has translated into an unusual number of homes that show as withdrawn or canceled listings. A few others are simply letting the listings expire.
So, why are sellers doing this? Primarily because buyers are asking too much of a discount. Instead of 5-10% some buyers are asking for 20-25% off the list price. That's unrealistic for most homes but a few have been sold at such a steep discount, which encourages buyers to ask for more. However, a large number of sellers don't have to sell. Which is why they're taking their properties off the market and waiting.
My advice to buyers is not to be too greedy. There are great deals to be had, just don't expect a fire sale.