How badly is CentOS hurting Red Hat?

Why does Red Hat tolerate CentOS? The Community ENTerprise Operating System is an identical binary clone of Red Hat Enterprise Linux (minus the trademarks), compiled from the source code RPMs that Red Hat conveniently provides on its FTP site. It is also completely free, as in beer. CentOS provides no paid support, but it does track Red Hat updates and patches closely, and usually makes them available within a few hours or at most a few days of the upstream provider, which it refers to for legal reasons as “a prominent North American Enterprise Linux vendor.”