Prosecution is also a form of punishment
I'd like to see something about the disproportionate disruption to peoples' lives be taken into account on this as well.
Let's say that McKinnon's situation has been reasonably fairly represented as minor and probably in the uk for a first offence liable to lead to, say, a fine of around a thousand and couple of hundred hours of community service. I'm not saying that this is necessarily appropriate in this particular case, it's a for-instance argument. That's a substantial punishment for many people.
But as a punishment it's nothing compared to the harm and stress that would be caused to all but the most extraordinarily resilient person by their forcible extradition and then prosecution in a foreight court along with the total disruption of their life, employment, family and all the rest. For the ordinary person you are going to lose your job - certain. You have a house and mortgage? Oh, bad luck on that one, but hey, if you get off you'll be back in two years, no harm done, you will be able to pick your life up again. Your wife left you while you were on remand in the US and has taken the kids? Bummer, but it's easy to produce kids, just get another woman you love.
Now I know that that's not appropriate in this particular case but surely only the most absolutely heinous kind of crime should even be considered suitable for extradition? The process itself is a ghastly form of punishment that you receive whether guilty or innocent.