I don't tend to circumvent geographical restrictions for price reasons in any other shop but Amazon.
On Amazon, I do it, and I do it a lot, for the simple reason that ebooks - whether by US or UK publishers - are considerably (and I mean by $4-7 on average for books at their regular price) more expensive for me on Amazon than they are for my German, French, Irish or American friends.
If Amazon (and yes, here I'm also putting some of that blame on Amazon) feels it right and justifiable to add their $2 surcharge (which also means an increase in the amount of VAT they add to my book purchases) to the price of ebooks bought by people in certain countries (many of those being countries with considerably lower average income levels than the countries in which that surcharge does not get added), then I don't feel any particular moral guilt in circumventing that.
Perhaps if I had a 3G capable Kindle and used Amazon's "free" 3G to download my books, I'd feel differently, because in that case I could at least see some reason for that surcharge. As it is, I don't even own a 3G capable Kindle device, and neither am I robbing a local publisher (since there is no local publisher responsible for publishing foreign ebooks in English for my market). I'm not living in anyone's target market, really, so if I pretend to live somewhere that is a target market (and, incidentally, do my part in helping to push a certain book upwards in the bestsellers list for that market/region, which apparently sometimes matters to publishers and authors?), I'm not really overwhelmed by moral guilt.
And yes, I know I'm breaking some kind of agreement or another, and justifying this to myself comes down to, well, justifying my behaviour to myself, but with the price differences (and income differences) being what they are, it also comes down to me either buying books from an official shop at a price the publisher and bookseller have deemed appropriate in their desired target market or not being financially able to buy those books at all, resorting to either torrenting (which I'd rather not do) or not reading them at all, neither of which will be particularly helpful for the authors and publishers concerned.
A typical "genre" book (a year or so after release) on Amazon costs e.g. $5.76 for people in France or Germany, $7.99 for Americans at regular full price (and often $1.99-2.99 as a daily/monthly deal) and $11.49 for me - this is not an insignificant difference when one reads over 100 books a year and has none of the ways people in the US or UK would have to read the same books for free or cheaply, i.e. to borrow it from a library or from a friend or buy a cheap used paperback.