Sorry, can't address your question about backing out of an accepted offer, as it totally depends what conditions you named in your offer, and your local legislation.
But, we did buy a house unseen as our primary residence when we moved across country nearly 8 years ago. (This is roughly analogous to moving across-state in the US)
caveats:
1) I also had family who could do a walk-through, one of whom owns a lot of rental property in the city. I asked him how much he'd pay for the house, and that was what we offered.
2) I had grown up in the city, so already knew which suburbs etc I'd be ok with living in, and which I would not.
3) It was a pretty standard post-war brick and tile house, so no big surprises with layout etc (although, one of the bedrooms turned out to be an add-on, with no basement or roof access, and near impossible to insulate. Still not a deal-breaker for us, though).
4) We're both pretty mustachian and pragmatic, and neither of us had big dreams or non-negotiables about what had to have/not have in the house - big enough bedrooms for the kids to share and our King sized bed to fit, and a non-pokey lounge with good light were about it. Otherwise, we didn't really care about aesthetics or age or style of house.
5) We got lucky. House was built by a builder for himself (so solid as a rock), heaps of built-in storage, the house had had ONE owner its entire life, so no dodgy stuff that nobody knew about, and it hadn't been altered, re-altered, re-altered until who knows what was going on.
We stayed 7 years and only moved when we discovered we're expecting another baby. 4 kids in 2 1/2 bedrooms just wasn't going to fly for us.
In the last 7 years here, people have gotten a LOT more cautious about buying houses, and it is standard to get a building inspection as part of the sale - so the offer is usually made subject to finance, building inspection, council record inspection, insurance being obtained, AND an electrical inspection. (Huge earthquake in a city here a few years ago has put the frighteners on the insurance companies, and they often have conditions before insuring - like a clean building report and electrical inspection).
If I was offering site unseen now, I'd get all those inspections done by registered professionals, AS WELL as having family walk-through. And even then, I'd only rely on the family opinion if they have financial skin in the property game at the time in the same city.
