A lot of energy is going into this discussion about saving 25 lbs!
Which
may represent a fuel economy difference of about 0.25% - 0.5% based on the oft quoted figure of a 1-2% fuel economy penalty for every extra 100 lbs carried (EPA).
As Dan knows, you can gain an equivalent weight advantage by just not filling your tank above half way.
I've only ever had one instance where I had to change a tire, and it was my own fault: I was driving too fast on a road I didn't know, at night, in rain, and missed a turn. I wrenched the steering, oversteered a bit, and smashed the rear wheel into an icy snowbank on the roadside, breaking the bead seal. The tire itself wasn't damaged, but I didn't have a 12v compressor then, and even if I did, it may not have fixed the problem, depending on how far the bead was off the rim (don't remember). But I did have a spare.
The main issue seems to be: if you have a blowout or failure that you can't fix with goop or a plug kit, and you have no spare, then you're out of luck. (Unless you also have a roadside assistance plan.)
Alternatives in worst case, no-spare scenario: put the blown tire on the back (if it isn't already), and drive slowly to where you can get it replaced. Is this reasonable? My car weighs next to nothing, so I kind of doubt I'd wreck the rim, but I don't know that for sure.
Another option: leave the spare in the car for highway trips, where the weight savings benefit is minimized and the inconvenience of a flat is maximized. Take it out for local driving where the weight difference will pay off more.