seizure - i think this is unlikely, but some people recommend physical gold and look after it yourself for this reason.
I don't do this because
1. i don't want to store gold in my home or in a deposit box
2. if you do want to sell quickly, it might be more difficult with physical.
BullionVault.com - you can buy gold in their New York, London and Zurich vaults - many people go for Zurich due to it being the least likely to be seized. I have some in both London and Zurich.
When to buy/sell I think we all worry about that, also the % of your wealth to allocate the gold?
The worst case scenario of a massive collaspe in the POG, I *hope* would only happen after an obvious bubble like growth.
Thinking of owning some gold as an insurance policy against eveything going tits up gives me some comfort.