The reason the avian flu is a big concern is because of the nature of the influenza viruses. The flu kills because you cannot rely on previous immunizations (vaccines) given every year as the infuenza virus is the classic chameleon which is studied intensively for its ability to rapidly/instantly adapt to formed antibodies against it by raising new epitopes and antigenic variations. It is for this ability to change itself that we worry about an antigenic drift from an ability to latch onto pig or bird (avian) respiratory linings, to an ability to latch onto human respiratory linings. It is precisely because of this that drugs like Tamiflu and Relenza will be useless in the near-term and long-run. It may save the life of a couple of people, but in the intermediate term, even those people whose life it saved will again be under attack by a variant/newly evolved epitopic form of the virus.
Short answer: Don't worry about stockpiling drugs - they will be useless to you. The drug companies might make a few bucks in a run on them so only they would benefit.
For people who want a more detailed explanation about the influenza virus physiology and the whole antigenic drift idea check out this link.
http://users.rcn.com/jkimball.ma.ult...Influenza.html