And Google notified them last week that Google was dumping Clearwire stock. Maybe the Board of Directors realized that Sprint may need that cash to bail out Clearwire once again and that they couldn't do that and buy MetroPCS at the same time.
The way it sounds, there wouldn't be much cash involved anyway. Sprint would give out shares to MetroPCS who'd now own 30% of Sprint - that's a lot of paper-money right there.
Either way- all these cell mergers should be stopped at any cost. This is already an industry where competition is almost non-existant and it's almost impossible for new players to enter the market - the last thing we (consumers) need is mergers.