Although GA does provide nice statistics (for free), I recently ripped all of my GA code out of all of my sights, since I noticed a real disturbing occurrence — my site response times have gone in the toilet since I had added GA to them. Moreover, it is rumored by many close to the scene, that Google now considers response time, as part of their overall algorithm. I have reverted to my old analytics (perlonline.com) – this is not a paid endorsement. For a $ 10 flat fee, it gives me 80 % of what I need. This is a quick-and-dirty stats solution, and doesn’t involve any opt-in/opt-out choices on the part of the user.
To answer the question, it most certainly will effect webmasters, when people can choose to opt-out of this function. Anyone concerned with privacy issues over the Net, will always choose to do so.