Above 50%? The threshold for not supporting IPv4 would be far higher than that. Think about how long it took to for companies to stop supporting IE6 when there

Above 50%? The threshold for not supporting IPv4 would be far higher than that. Think about how long it took to for companies to stop supporting IE6 when there was still only residual usage. The effect of not supporting IPv4 would be far worse as well - not just a buggy looking site, but zero functionality.