April 16, 2014
Disclaimer: I have not worked on Google Flu and have no inside knowledge about the project.
tl;dr Saying that Google Flu doesn't work is a bit like pulling up a spam classifier trained on data from 2009, applying it to spam today, seeing that the results are pretty shitty, and then concluding... well, Bayesian classification doesn't work.
Recent reports have concluded that Google Flu "doesn't work". See for example an article by Lazer et al. and a piece by Steven Salzberg. This is cited as an example of "big data hubris".