I call it "Upgraditis". You start out by cutting all your ties to the new fangled, hyped up products out there that supposedly make you ride better. You want to simplify your life and your riding. You decide on converting an old bike you have in the basement or one that you hope to find at a thrift store into that rigid singlespeed or fixed gear bike. You research online on how to convert your ride and try to do so using only the parts available to you in your used parts bin. Soon you're riding your new found friend everywhere, enjoying every damn minute of it. The silence of no derailleurs, the ability to concentrate on conquering that hill rather than on what gear you should be in. You're in heaven. Pure bliss. But somehow, something just doesn't feel right. You tire of having to adjust the Singulator on your SS or you're tired of your rear wheel slipping in your semi-horizontal drops on your fixie. You muster up enough cash to have fork ends welded to your frame. Now, that seems better. But then your SS's rear wheel, with spacers to adjust your chainline gives up. Or your Loctite and BB lockring won't hold anymore. Quick phone call or online purchase and you have yourself a new rear wheel. Heck, you even bought a matching front. Now your cranks are getting old so you upgrade those. Soon you're eyeing Spicers and Independent Fabrications or deBernardis or Iros or Milwaukee frames. Plastic toe clips suck. You upgrade to Egg beaters or top of the line clips and double straps. Soon your custom frame is being made to your specs and your specs only! You've come down with Upgradeitis!
Or you could keep buying thrift store bikes and upgrading, or shall I say, replacing parts as they break with new to you old parts from the LBS's used parts bin.
Either way, new parts or old discarded ones, a fat ass ain't gonna get you going faster. (Well, maybe on the downhills, but I digress). Whether you ride for fitness fun or to show off your new ti something or other, the factor that ties us all together is we all ride.