In Uzbekistan I was stopped, searched and questioned six times in one day.
At the border with Tajikistan, one official tried hiding my paperwork to elicit something from me.
In Kyrgyzstan, I was physically harassed and detained by the police, and about US$30 taken while they searched everything on me and a Dutch backpacker I was going to get food with.
I'm not particularly dodgy looking - it's happening to a lot of backpackers I meet. Tourists are apparently a prime target for corrupt officials.
Any suggestions or tactics for avoiding these occurrences? Aside from carrying only photocopies of your passport so that they can't hold your passport ransom, I've not heard many successful tips...