People have a tendency to find ways to "waste time" no matter what methods are available, be them television, social networking, or video games. With that said, I don't think watching television is always a waste of time. If it is done for enjoyment, it's not a waste. A person will gain pleasure from that if only for that moment. If it's done for educational purposes, it's not a waste. A person will gain knowledge of some sort from it as long as they do not watch passively.
Even shows that seem like a waste of time can provide some sort of education or benefit to the mind if a person watches it right. When I watch reality shows, which are my guilty pleasure but I consider "trash" television, I tend to think about the social interactions and think critically about the situations they have been put into rather than just get sucked into it and think what the producers want me to think. Is this better than reading a book? Probably not, but I enjoy doing it every once in a while.