Nobody forces you to use the Internet... yet. When capthas are used too much, people will protest by not using captcha sites. I think Bitcointalk.org may have reduced the strength of their login captcha, already.
How many people would even get on the forum if they had to do a captcha every page that they wanted to look at? Things will self-regulate by the law of supply and demand. I mean, if nobody came to Bitcointalk.org because they had a login captcha, and if their total hits dropped down to zero because of it, they would get rid of it in 5 seconds.