[chris_dcosta]

The answer to your question is in the the question - which means you almost get it.

You are adding an additional variable: for example "liking iTunes or not" that can't be tested like this, so you are confusing yourself as to the meaning of the results.

You are also trying to imply meaning on the "not doing something" aspect of it "does that say anything about the alternatives". This can only be true if the alternatives are available at the point of selection. Therefore, you are right this says nothing about the alternatives.

If you really wanted to see which was the preference from all three then all three choices need to be available to choose equally. At the moment by only giving one albeit random choice you are not answering anything.

To understand this process better think of the classic "google blue" test, where the colour of the links in the search results was subtly changed for random users to find out which blue worked best.