The Internet is arguably the best representative of public opinion. And here's why.
All right, so it's not the only medium out there. But take a look at the competition.
Newspapers - Much read, much maligned. With good reason. They often grab hold of a story that twanged the public interest once and hold on to it for dear life. Many of them only deal with recent developments of relatively high-profile issues, missing out the small changes in the little issues that people take an interest in. And most significantly, each gears its stories towards a particular cross-section of society, rather than society as a whole.
Newspapers / Magazines
Magazines - better judges than the papers, but tend to forget that looks aren't everything. And that beauty is in the eye of the beholder. Not to mention that there are other factors that attract people; like what they do, or fictional characters they are associated with. Also deals with a specific rather than general audience.
Producers and show creators are constrained by the bounds of money and originality. If it's too expensive, they won't use it. If it's too unoriginal, they'll lose ratings.
The Internet, on the other hand...
...has fan sites. There are a lot of these. You really can't avoid them. And they're cheap and unoriginal. But who cares? You've got an interest in something / someone, bordering on an obsession, bordering on a court restraint order. Being a social animal, you want to share it with the world. Now you can. You do a website on Star Wars or Sarah Michelle Gellar and watch the hits roll in.
These sites are about what these people want them to be about. Not, for the most part, what they think others will want to read.
Which is why the Web is a better way to gauge public opinion. It's essentially like the sort of thing people say in pubs / bars. Confidential, free, reasonably honest opinions.
Problems with this
How do you work out how many sites there are for a particular subject?
Search engines don't give the whole story. But there are often votes on people or topics around the Web, and one fan will find out about it and mention it on his / her site, and the word will spread pretty quickly. So a large proportion of the fans go and vote. Which is why Sarah Michelle Gellar wins Internet polls when other people win them in magazines.
Another problem is of course that the Internet is not universally used. But it's getting better.