More often than not, a domainer (domain investor) will submit an initial low ball offer to find out what the seller's actual asking price is.
The seller then gets frustrated with the continued stream of low ball offers an replies with an ask price well above what they may be willing to sell the domain for.
With regards to Sedo, it would be nice the have additional communication options so that buyers and sellers can work out the price while keeping the transaction on Sedo.