I think many here would agree that we prefer to do our own work, or would have handled the situation differently. I sure as hell like to think that I would have caught something like this before it slicked my rear tire and took me down.

None of that removes liability from the shop that was paid to do the job. The fact that a customer is qualified to do your job, does not make it okay for you to do a shitty job, especially when doing so can foreseeably put someone in serious danger.