Osama Nasr was abducted by the US from Milan, Italy in 2003 without permission or cooperation from the Italian government and tortured in Egypt. Illegal abduction can happen anywhere. I agree publicity would make it harder, but the US has shown willingness to act extra-legally and ignore the fallout even from allies (Pakistan, Italy etc), so Snowden is probably not safe anywhere, just a bit safer for longer in a country which opposes the US. In his words:
You can't come forward against the world's most powerful intelligence agencies and be completely free from risk because they're such powerful adversaries. No one can meaningfully oppose them. If they want to get you, they'll get you in time.
This happened just two years ago. Palestinian engineer, traveling in Ukraine, was captured by unknown people, and was found in Israel prison week later.
The US government has all the time in the world and in months/years from now when nobody remembers his name there will be an opportunity for a extradition to be done quietly.
http://en.wikipedia.org/wiki/Mordechai_Vanunu