[Xaccers]

Yes, but heavily restricted and monitored, for educational use, and not in their cells but in an IT room.
Personally, I don't think TV's should be in their cells either, if they want entertainment, read a book (if they have trouble reading, then reading a book is probably the best thing for them!).
Have a TV room.
Much cheaper to provide 1 TV per TV room (1 per prison would be silly considering how many inmates there are these days), likewise with providing computers in IT rooms rather than every single cell.
You also have the issue of security for repair staff.
A single room can be closed off for extended periods of time to make major repairs without having to worry about what to do with inmates.
The same can't be said about a prison cell. If the inmate can't be in the cell, they need to be somewhere.
Internet access has been used by several inmates to show that they were wrongly convicted.
It's also a good educational tool which is part of rehabilitation.