Vee is actually for signals that has both a positive and negative part. Look at a normal waveform and you can see that part of it is "under" the GND level. Vcc is feeding the signal during the positive part and Vee feeds the negative part, that would be the simple explanation. For TV this is not something to care about becasue all TV signals are on the + side of GND but to make the 4051 behave you have to connect Vee to GND. The problem with the on resistance is not really that big unless you are planning to load the camera with a low ohm (z) equipment, most TVs are 75ohm. The higher current you use in your cable the more you will loose inside the 4051. One the other hand if you want to place the camera far away from your TV for example make a CCTV system for you house it is possible you have to put amplifiers on the cameras to boost the signal if the cables get really long. How long is really long? Well that depends on how cheap your cameras are, some has really strong internal buffers and some are so weak that even the shortest cable makes things starting to fade. It is possible to make a simple video amp with a simple OP-amp so it is not that hard to fix if you later see you have a need for it.

One more advantage of 4051, cheap... really cheap so you do not risk alot by testing them.