If a coin has some pitting is it worthless? What does pitting mean exactly? http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=190455623637&ssPageName=STRK:MEWAX:IT There is an example.
When someone says a coin has pitting it means the coin has suffered from corrosion and there are small holes in the surface of the coin. Just like that Buff you linked to.
It depends on the coin. For US coins, it has a significant affect on its value, especially more the newer it is. Most 20th century US coins are valueless if pitted except for some keys, and even then they are much reduced in value. For ancients, we live with this all of the time. Some issues are simply not available unpitted, so the price is not as affected as much. If you ever see "smoothed" that means that someone has smothed out the fields of a coin to reduce the effect of pitting. Of course this is considered the same as tooling, which is adding details to the design, and either of them lower the value of the coin.
Pitted early coppers are the only way some of us can afford those kinds of coins. A scuzzy pitted coin may be worth 30-50% of an average condition coin and still be worth around $50-$200 dollars
Typically pitting causes a drop in price of 50% or more. Early large cents are a bit of a misnomer, as a far larger % of them have these types of problems, and there is still an active collector's market in these "problem" coins. For buffs, I would expect more of a 75% drop in price -- less for a more rare coin, and more for a less rare one.
