What countries are not competing in the 2012 Olympics?

Answer 1

11 countries do not compete in the 2012 Olympics:

Abkhazia

East Timor (Democratic Republic of Timor-Leste)

Kosovo

Nagorno-Karabakh

Niue

Northern Cyprus

Sahrawi Arab Democratic Republic

Somaliland

South Ossetia

Transnistria

Vatican City (State of the Vatican City, Holy See)

In addition, South Sudan (Republic of South Sudan) does not have their own National Olympic Committee, but they are competing under the Independent Olympic Athletes banner.

There are 207 countries in the world at the time of the 2012 Olympics, 196 of which are competing. See reference questions linked.
I don't no cause I'm in a lol

(land of lollypops)
Kiribati, Afghanistan
Vatican City, Kosovo, South Sudan
You can bet North Korea and Myanmar will not send athletes to the Olympics.
Bulgaria is not participating in the 2012 Olympics.

Answer 2

A large number of countries did not win any medals. The related link lists the 85 nations that did win Olympic Medals

Answer 3

10