The only people who make threats like that are those who have a nice library of a few dozen or so pirated games on their machine.
I doubt that. A lot of people don't like Steam for a variety of reasons. Like, for example, they've never downloaded a game off of it. The first time I used a Steam game filled me with trepidation as well. But once I had Portal up and running, I've avoided box games ever since.
An a WHOLLY UNRELATED NOTE, I was at a record store sometime this summer, and the guy working there was talking about how, not only do VHS tapes have a larger library than DVDs, but they actually offer such a higher picture quality as well - and they last better and are easier to use!
For some people, things being old and unwieldy is actually a bonus. Learning to program a VCR is an achievement, learning to use Netflix Instant is brainless. So it hurts when the work you put into learning to get your VCR to work has been made valueless by the relentless march of technology.
Wonder how much you can take off by people not buying it as a result of Steam.
But I assure you, I wasn't the only person who said "Oh thank God, I can just buy it through Steam" when the announcement was made. Obviously a straight comparison is impossible, but all the indications are that companies gain far more players than they lose from that particular migration.