Bryan over at EconLog has an upbeat assessment  of TV watching by young children:
Yesterday my baby acquired a valuable life skill: He learned how to watch television. I’m thrilled for at least three reasons:
1. Television is fun. I don’t want my son to miss out on one of life’s great pleasures.
2. Television is a cheap electronic baby-sitter that allows parents of young kids to get a much-needed break.
3. When my son is older, the threat to deprive him of television will become one of our most convenient and effective tools of discipline. The naughty corner ‘s usually enough, but when bad behavior persists, it’s time for a night without t.v.
Won’t t.v. stunt my baby’s cognitive development? Hardly. Twin and adoption studies find zero long-run effect on IQ  of all family environment combined. Television’s isn’t just a drop in the bucket; it’s a drop in a bucket that doesn’t hold water.
Readers of my book, The Invisible Heart  will remember that Sam Gordon’s perspective (and mine) are a little bit different. I’ll note first that you can replace the word “Television” with “single-malt scotch” and the same logic applies.
Our kids watched virtually no TV growing up and to this day as they range in age from 10 to 17, they watch no regular network televion during the week. We do watch a few quarters of football on Sunday. But that’s it.
We spent a lot of hours reading to our kids. They all like to read. They also like to amuse themselves in a variety of non-TV ways. I think those are good things.
Finally I would point out that studies that relate the family environment to various outcomes (IQ, criminality, happiness) are not experiments where people parent in random ways and the results are observed. People parent as best they can. The fact that there is little relationship between parenting strategies and outcomes does not mean that ANY parenting strategy will have no effect.