Facebook have recently updated the formatting of the news feed on their website. One of the changes is the reduction in the size of the font. In my opinion, this is too small for me to comfortably read. I cannot imagine how those with reduced vision are able to read the text without straining their eyes. From a usability standpoint, I don't think that this was a wise move. I am assuming that the reason for the change was to fit more elements onto the page, but this could be done without changing the font size or without reducing it as much as they have.
There is an article about the change, and Facebook explains that the change is an experiment (1). Hopefully, the feedback received from users about this change will make Facebook reconsider.
(1) Gaudin, Sharon. Facebook users squint at font size change. http://www.computerworld.com/s/article/9194920/Facebook_users_squint_at_font_size_change [4 November 2010].