We prove that there exists an absolute constant \delta>0 such any binary code C\subset\{0,1\}^N tolerating (1/2-\delta)N adversarial deletions must satisfy |C|\le 2^{\poly\log N} and thus have rate asymptotically approaching 0. This is the first constant fraction improvement over the trivial bound that codes tolerating N/2 adversarial deletions must have rate ... more >>>