A big reason to buy a bicycle from your LBS (not parts, clothes, etc.) is that they will work with you even months down the line in a timely fashion if you experience problems, be it mechanical/fit/warranty/part replacement/service/whatever, and will often exchange parts such as stems, handlebars, seatposts, etc. for little or no charge. They will often also do a fit of some shape or fashion, esp. if buying a higher end bike. If you're buying a gmc denali, lowest bid wins. If you're buying a prince or an r5ca, do yourself a favor and buy from a person in a brick and mortar shop. (I realize these are extreme examples)