My experiences buying and selling stuff online has been mostly positive. Craigslist around here is good for buying but poor for selling stuff like sewing machines and supplies. Ebay is good for getting a decent price for possesions if one is conscientious in selling and shipping. A big part of the problem with ebay is people are selling sewing machines who have no buisiness doing so and are only interested in the bottom line with no concern to safe shipment. These sellers need to be "marked" so we can avoid them and help save some nice machines. Leaving negative or neutral feedback is important for doing this.
Jon