PS4's biggest weakness, eh?
It's probably the fact that Sony is the least financially stable company of the three console manufacturers. Nintendo can survive on it's 3DS holdings and cash reserves alone if it has to, and Microsoft makes money via Windows and the MS Office Suite holdings.
Sony is a hardware company, and while the Playstation brand itself is doing well, Sony overall isn't doing so hot. Hardware is just a riskier business than overall software portfolios.







