Nat. Biotechnol. 27, 980–983 (2009); published online 24 September 2009; corrected online 6 November 2009; pdf corrected 5 February 2010

In the version of this article initially published, the email address for Ben Bonifant was incorrect. The email address is bbonifant@campbellalliance.com. The error has been corrected in the HTML and PDF versions of the article.