Well, if you talk about Bitcoin etc., it's a gold rush situation - high risk/high reward situation which is strictly voluntary, so I see zero issue with that, on the contrary, I see it as excellent experiment which, unlike many other social experiments, won't bother you at all unless you opt in.

With Uber/Lyft it's trickier since while you are welcome to not use it, it may have implications which are beyond direct users of the services. Still, I think the effects are relatively small and not disproportional to what you could encounter without them - i.e. how badly you can be burned there? Surely, you can have a bad driver - same could happen with a Taxi. A bad Uber driver could create a bad situation on the road - so can any other bad driver, nothing new here. So marginal costs are pretty low here. Not to defend bad drivers - those should be dealt with appropriately - but the additional "burn" that would be caused is IMHO pretty low.

I'd say the big externalities affecting non-customers are increased congestion and a questionable insurance arrangement. There are also the handful of cases of sexual assault and similar that have happened that arguably could have been avoided with background checks, but perhaps the incidence of these is small enough that you could write it off.

Is there really big change in congestion? If not Uber, people would take a taxi or drive themselves - that's what I'd do. Both cases don't reduce congestion.

As for insurance, there are tons of people on the road with bad insurance, at least for Uber as I understand you have something to back it up.

As for assaults and other bad apples, that could have happened with taxi too. I don't believe any company of these proportions could have checks that could 100% prevent such cases. I'm not sure it's possible in even in principle...