Some in the music industry wonder if digital music sales have reached their apex.
Some old fashioned music promotion tricks that need to end:
1) Releasing songs on different dates in different countries.
2) Making songs unavailable for purchase outside of certain countries.
3) Releasing songs to the radio months before they are available for purchase.
4) Album-only tracks on iTunes--always a guaranteed deal-breaker for me (shades of unscrupulous record label tricks from a decade ago, in this case the "single for which there is not actually a single available, so you have to buy the full-length in order to get the song").
I think the first three all fall into the same general category: each of these practices encourages people who have been "shut out" or who are anxious to acquire a song to go looking for a pirated version online. We live in an age of on-demand gratification; if I know a song is out there, I should be able to buy it. If I can't buy it, I'll steal it, since it's quite possible the song I am enjoying will NEVER be legally released in my country anyway.
Regarding releasing songs to the radio well in advance: this "whetting the appetite" theory seems a bad one. The longer you "whet the appetite" without offering the song for sale, the more likely people will lose patience and steal a good quality digital radio-rip. I imagine radio stations are direct sources of many leaks, also.
It would be interesting to see a study tracking the spread of a particular MP3 around the world. I recall that the Atlantic magazine once did something like this, where they tracked a pirated movie.