Some of the possible indications that you might see when you have the blue blinking light issue other than the blue indicator light blinking are no video/audio output seen on your TV and the console powering off after the console does its blinking blue light thing.
Apparently there are a number of possible causes for the blinking blue light condition including: HDMI/HDTV compatibility issues, issues or problem with the PS4 power supply, hard drive failure in the PS4, or an issue with some other hardware component within the console.
To rule out an issue of HDMI/HDTV compatibility with the console it is suggested that if possible you try the console connected to another HDTV. Of course this seems obvious to us, but it is hard to say if HDMI compatibility issues are the major problem here, but it could not hurt to try before calling Sony or taking your unit back.
Sony is claiming that less than 1 per cent of the over 1 million PS4 consoles that it has sold so far are suffering with blinking blue light issues, but it is difficult to really get a handle on how accurate that might be. Only time will tell how truly wide spread the problem is. No question however that those who are having problem are not happy to say the least.