"I don't think TIGed frames have been around long enough for failures to really start occuring yet and there just weren't nearly as many racing frames with thin tubes and fillet brazed joints for a good comparison to lugs."

That of course, is one advantage of TIG, nothing is really around or kept long enough to be worth putting together with lugs. People ride completely new bikes every season or race. Longevity really isn't important any more. At some point though, when the aircraft factories were forced to give up gas welding in favor of TIG, for OSHA concerns, I'm guessing someone looked into the fatigue issues.

I spend probably more time in the Walmart bike area while the kids are buying Barbies, than I do in the LBS. I see all these dual suspension bikes for a hundred or so dollars, and look at the welding, which often looks pretty neat. I don't care if they are using slave labour, the consumable costs alone, make it improbable these bikes are being TIG welded. Some of them have several feet of aluminum welding on them. I suspect many of the "TIG" welded bikes we see are migged or robot welded, which doesn't mean they are badly welded. TIG is dependant on operator skill and there is a wide varience in the skill of various people who do it. Most consumers don't know this, don't know good welding from bad. Aren't aware there are master welders out there who produce a product that is many rungs on the ladder above the average "name" maker. To say that a TIG weld broke really doesn't tell us anything.

Bike building is a business with some full time makers, and a lot of skilled dabblers. Welding is a whole separate art. Unless a builder wants to also learn welding, the cost and skill curves are really too steep for welding. It does depend whether the builder is a welder first or a bike maker. I know some welders who can make a bike with cheaper welding technologies, but most people aren't in their class, and almost all bike builders are a little unimaginative about that kind of inovation, they just want to know what everyone else is doing.

Probably almost anyone could learn to weld a bike frame, there is a big difference between that and being good enough to teach yourself, explore until you find your own machine settings, and take the art to the point where you would put your house behind it. And in any case there are many place where you need a gas torch anyway in bike building so most people sign up for that alone since it saves them a few grand in tools. My welding hood cost more than my OA gas rig.

"I had neglected to remember that brazed frames are lugged, adding even more strength"

There is also the fascinating art of fillet brazing which uses braze as the joining material, no lugs. We have three comon methods: Welding, Lug, and Fillet braze. None is stronger than any other, since any one can be designed to be strong enough. There are great bikes being made in all three. Fillet and TIG have the advantage of unlimited geometry in the joints. But lugs are available for a lot of classic designs. Arguing about which is better seems to be dropping off in the frame comunity where some builder do both like Gordon, or some bikes end up using all three methods. Like for instance the Henry James MTB lug that uses a fillet for the chain stays. Or the lug guy who assembles custom lugs with tig. Custom makers are more banding together than fighting over this stuff any more.