There was a couple who were both imprisoned recently for running a 'business' cleaning up used stamps and selling them for a big discount to people who obviously re-used them.
Was it a crime? Yes, it deprived Royal Mail of legitimate income.
Should they have been punished? Yes, ideally having assets seized and otherwise suffering financially for their crime.
Are they the dangerous kind of people from whom society needs to be protected (at great cost to society) and who should therefore be incarcerated for two years? Personally, I'm far from convinced.
Stephen Gough (the Naked Rambler) has also spent time in prison. Yes, his hobby is extremely unusual, but are people like him really the best use of expensive prison resources?
I'm no fan of Jeffrey Archer, but I really can't say I slept much more soundly knowing that he was locked away from society.
There are some people who absolutely need to be in prison - for punishment and to protect society. Some of these people currently aren't in prison.
Even a short prison sentence affects the whole rest of your life - socially and financially - which can effectively end up as a punishment far beyond that due for a relatively minor crime. Non-dangerous criminals would do much better - for themselves and society - with community-based punishments: hard work and temporary embarrassment can be very effective.
It also seems to me that fraudulently and non-violently stealing a large-ish amount of money - especially from a large corporation or government, or 'society' figure (which is, of course, very wrong and to be punished) - or even defaulting on tax payments for whatever reason - is much more likely to result in imprisonment than violently stealing a relatively small amount from an ordinary, non-well-known individual, whose life will never be the same in many afterwards.
Similarly, government, big corporations and influential people can (and do) commit the most appalling crimes and are never locked up. Like with tax - some of the big boys get away with paying virtually no tax at all through creative accounting; whereas if one of their cleaners was also signing on, she would likely be locked up.
A soldier can be imprisoned and have their reputation utterly destroyed for a 'war crime' (and I'm not saying they shouldn't be); however, if you send countless soldiers to their deaths based on what you know all along to be outrageous lies....
Also, political prisoners, standing up for their beliefs - however worthy or misguided those beliefs might be. If they aren't inciting any violence or other non-peaceful protest, do they really belong in prison?
Are we only talking about imprisonment in the UK/West (not that we're immune from imprisoning people on political grounds)?
In summary, I would really want to know why somebody had been in prison and if they were genuinely remorseful and had fully changed their ways before writing them off as a completely bad cause.