Any electronic device can be affected by Electro-Magnetic Interference(EMI)
In short, no. LCD TVs and Plasma TVs will not be affected by any speaker without magnetic shields. The rear projection TVs won't have any issues either.
With home equipment, you will almost never see any problem with speakers causing interference.
The only time I've seen it was with some family. They had a large sound system with the biggest speakers next to the TV. They used "rabbit ears" for free broadcast. This had noticeable problems with TV signal only when the volume was high.
All our cables have shielding under the rubber case and are not affected by small magnetic fields from speakers.
The screen itself will not be affected. Only the old glass tube style had sensitivity to magnets because they actually used electron ray guns to light up the front of the tube.
The magnet would pull the electrons and distort the picture before it would hit the screen. They could also permanently distort the receptors on the front. But that's only with the old tube style.
I've heard that Plasma and LCD telivisions are not affected by non-magnetically shielded speakers. If this is true, no problem. If not, how far away from the TV should the speakers be placed so they do not affect the electronics of the telivison?
Also, what is a good rule of thumb for sub size as it relates to room volume? Looking for good, better, best advice.