The post above yours is proof, that people actually expected to be free.
And Valve is clear about it, too, but some people don't seem to be reading it carefully:
http://store.steampowered.com/freeportal/
"So you only have a few days to decide if your free copy of Portal is worth the price we're currently charging"
Which can be legitimately interpreted as "You have a few days to decide if you want Portal for free then it goes back to its regular price". Again, not saying that's the case but it IS a legitimate reading of that statement so try not to mock, mkay?