Well, as this thread seems to be well an truly underway (and, lets be honest, we haven't done it for a wee while) I can say that I personally think that a lot of tosh is spoken about dado heads (on both sides of the pond!).
Would I be right in thinking that if you are in the US the view is that it is right and proper and a human right to do whatever you want with a a tablesaw come what may, and that a dado is an integral part of that?
And if you are a Brit then the dado head is the work of the devil, every one in existence should be burned on a pyre and instant death is assured?
I think that the truth, if there is a truth, lies somewhere in Madeira, or at least somewhere else mid-Atlantic.
My own stand is that all the objections to dadoes are legitimate and that they can all be overcome.
Guarding. Any blind cut with a tablesaw means that a riving-knife-mounted guard needs to be removed. The temptation, therefore is not to bother at all and run the risk of using the blade unguarded. To do so is to underestimate the risk and to expose oneself to unnecessary danger. If you remove the crown guard, then use an alternative guarding arrangement then replace the crown guard afterwards. Personally I think that most crown guards, which have been around for generations, are very poor, passé, and much better options are available, even to the home woody, at little expense. I've written about home-made SUVA-style guards and one appears in some of my filming, for example. It's my current avatar, too.
The other aspect is momentum. A 1/4" stacked dado has twice the momentum of a 1/8" blade. Momentum = mass x velocity, so if we double the mass, the momentum is doubled too. But the weight of the blade is small compared with the size of the dirty great big motor inside my Excalibur 806. It does increase the stop time, but not by much. I'm still comfortably within the 10-second EU limit.
So it seems to me that the two primary objections are reasonably straightforward to overcome. I don't use my stacked head that often, but when I do I use it guarded and it gives me great service.
One of the arguments against, and it is a valid one in the real world, is that once a guard (or riving knife) is removed it doesn't go back on. Well that is not, it seems to me, an argument against the dado blade, it an argument against bad practice. Perhaps one against poor design of tablesaws. TS design is driven largely by demand in the US, and I'm pleased to see that new models are appearing with more modern design features - riving knives that are easy to adjust, remove and replace, blades that tilt away from the fence, switches that are where they are easily reached. Some day all saws will have these features.
The danger is that people with basic home-grade TS that was never intended to operate a D will think, "I can do that with mine" and fit a blade that substantially affects the momentum of the saw, they don't introduce appropriate guarding and carry out operations that expose the inexperienced to higher risk than is justified.
In such circumstances, stacked dadoes are, indeed, dangerous and should be avoided.
But I think it is more due to the nut operating the machine than the nut on the spindle.
S
