US operator Sprint Nextel is in danger of losing its first-mover advantage in next-generation network availability, with a Wall Street Journal (WSJ) report noting that its first WiMAX smartphone – the HTC Evo – is struggling with supply shortages. Citing estimates from Macquarie Group, the WSJ states that Sprint has sold 300,000 units so far, but manufacturer HTC hasn’t been able to keep up with demand.