Hi Glenn,
For some years now, the countries on the Arabian Peninsula have been working to launder improve their image. They have sponsored sports teams (for example, the Emirates sponsor a world cup racing boat; even though none of the crew are from there). They host sporting events (the Darfur race no longer goes across the Sahara, but is now run entirely within Saudi Arabia). Hosting conferences seems like just another opportunity for them to normalize themselves.
Suppose Oman, or any other country, says to ICANN something like (and I'm just pulling numbers out of the air here): Hold your conference here. We'll give your attendees hotel rooms at half what they would pay elsewhere. We'll give your staff rooms for a quarter the rate elsewhere. And we'll let you rent the conference center for 10% of what you would pay elsewhere. That's going to make them look irresistibly attractive.
Even if you are monitoring the human rights records of possible venues, at some point organizations are going to see a tradeoff. They probably won't go somewhere actively dangerous to their attendees (e.g. Khargiv). But human rights abuses would have to get pretty dire before they would out-weight any and every other factor.
I'm not saying that the IGF or ICANN necessarily made that calculation. But I would be surprised if the cost factor didn't factor in.
Bill Jouris