This is a real concern, and so far, it has not happened that often but even from the beginnings of the recent pandemic, there were already cases of people who had NEVER been treated with Tamiflu yet, the virus infecting them was found to be resistant to our current frontline drug, Oseltamivir (Tamiflu) for treatment of influenza. What will we do if this becomes more widespread? Don't think that this could happen? It did happen already with seasonal H1N1, and relatively quickly too with the seasonal H1N1 strain that preceded the pandemic flu.
Dr. Niman's post are considered to be somewhat alarmist at times, but he does makes some interesting points. Best to read his entire commentary which might not be easy, but you can most likely get the gist of it.
Quote from www.recombinomics.com
The striking parallels between H274Y spread in seasonal H1N1 in 2008 and pandemic H1N1 in 2011 strongly suggests that H274Y will soon become fixed in pandemic H1N1. Like 2008, the spread is driven by clonal expansion and not selection through Tamiflu treatment, which is why the latest comment by WHO on sequences in Japan is cause for concern. The clear clonal expansion is ignored in the WHO update, and instead reference is made to a linkage between the detection of H274Y and use of Tamiflu by the corresponding patients. This disconnect between the sequence data and the WHO announcement raises serious competency concerns regarding those responsible for this conclusion / announcement.
The lessons learned from the fixing of H274Y in seasonal H1N1 were clear and the failure to relate this pattern to pandemic H1N1 is alarming.