We mitigated these sorts of issues in TicketStumbler by having clearly-drawn lines for who was responsible for what. This was easy for us because we had a two-man team consisting of one technical person (me) and one business/everything else person (Dan). I would occasionally explain technical decisions to Dan, especially if they were going to take a while to implement (rewrites, etc.) This had the added benefit of forcing me to talk out an issue and better justify it to myself.

This made for some fast decision-making. The only downside has been that following his death I am still being charged for services I wasn't even aware we had and for which I have no non-violent method of cancelation. However, this is obviously a rather extreme edge case that most people won't have to deal with.

The main issue highlighted in the post regarding cell plans is a bike shed-style decision. These are problematic because anybody can take a few minutes to research the space and come up with valid arguments for/against another person's recommendation. Generally, the best thing to do in these cases is to simply defer to whoever broached the topic and have them make a decision; they had a head start on research and cared enough about it to bring it up so it makes sense for them to own it.