Sawtooth traces on a PCB
Sometimes snake traces are used to ensure that parallel traces for a data bus all have the same length. This minimizes the phase difference between the signals. I can't see very clearly in the picture, but if the traces are smooth curves I'm betting this is the reason. 

These are typically only used in very high speed designs where tiny signal delays and phase differences make a difference, the HDMI interface probably falls under that category. Also as mentioned below, differential signaling is another instance where phase differences between the signals can be very detrimental.