My question to you is why are you considering a low ball offer? Is the property "troubled" in some regard(condition, location, etc)? Is the immediate area suffering from an undue number of foreclosures?
Most people derive a lot of pride and self worth in the ownership of their home. This emotional aspect is critical to how well your offer will be received if the seller is not under overwhelming financial duress to sell.
With the price corrections to many real estate markets around the country and daily reports of this all over the media, buyers are no longer self conscious about submitting a less than asking price offer, particularly on a property that has been in the MLS for a lengthy amount of time. However,unconsciously, many homeowners will interpret such low offers as a valuation of their time and experiences in the property.
I concur with Mark...make a market based offer and you are apt to get the best out of the seller...anger them, and it will negatively color how they deal with you for the entire transaction.
I have sold ten's of millions of dollars of Cape Cod Real estate over the years...I have never seen a truly "low ball offer " work for anybody...Most sellers now expect that they will get less than asking, but are not prepared to give away their properties on the Cape. Money is cheap, albeit more difficult to borrow right now...paying 10% more than you wish to right now might be the most prudent move.