This is getting disturbing
Like I said in my rant earlier this stuff is not easy to get ahold of at least not in the quantities we keep seeing. It is certainly possible that one contaminated individual spread it to all of these places. It is even likely that the reason that they are keeping the "witness" away for a bit is because they are worried that he is contaminated and it will be somehow detectable. (it would have to be a lot for an Alpha emitter to be detectable and just sloughing off to be swiped later).
According to information leaked from the post-mortem examination, Litvinenko died from a dose that could cost 30 million euros. This seems a bit too rich for a murder. - This seems to actually be very reasonable dosage estimate to me considering the rapid onset and the total bodily system collapse he had. To loose his hair from an alpha emitter in just a week would take a huge amount (radiological speaking).
To get this level of cross contamination of detectable levels of Polonium would take a nations involvement or some heavy duty terrorist type organization. The quantities would have to be huge (in terms of activity not mass or volume) To head off the normal anti US conspiracy buffs (idiots) the US (and all of the Western nations) tracks its contamination sources very well. There would be a easy to locate paper trail.
I don't usually get into politics on this blog or conspiracy but the radiological angle makes this one interesting to me.
and suggested that if a Russian intelligence agency had wanted to kill him, it would have been foolish to use polonium because its source could probably be traced. - The last part of this is partially true. Normally isotopes have a "fingerprint" that can be used to trace their origins. Polonium though makes this more difficult because it's final decay product is stable. If it is pure enough it probably couldn't be tracked and the minuscule amounts would make it even harder.
I think the Russian government is the obvious suspect but people should also be worried about his possible Chechen connections. I normally debunk the dirty bomb junk I hear but his possible connections to some radical elements (on both sides of the equation) and the presence of this much hard to obtain radioactive substance has me scratching my head.
I hope some really good people are chasing down all of the possible threads on this one because some of the potential implications are pretty scary.
In any case this was clearly all just off topic speculation. Interesting speculation but still just guess work.