I could begin with a few thoughts.
One of the interesting phenomena about FOI is that very few people actually use it; fewer than one in a thousand people make an FOI request. It's still a lot, but not a lot as a proportion of the population. Most people find out about freedom of information via the media, mainly via the mainstream media, whether that's in physical form or online.
In terms of people's sources for information, as far as I know, the majority of the population still use the mainstream media. However, more and more people are using blogs. One interesting thing about FOI is that it also gets onto blogs, and lots of journalists who use freedom of information, if they can't get their story in the press, will use blogs to publicize that information. There's also been some high-profile use of FOI by certain famous bloggers in the U.K., among whom one of the most famous is called Guido Fawkes. So there is an interaction between social media, for example, and freedom of information, and using that as an alternative source.
I suppose the negative effects are in a sense in the eyes of the beholder, really. One of the problems with discussing freedom of information is that I think there is a hidden bias in it when you speak with politicians and officials. To quote a very good U.S. study of transparency, to the politicians and officials freedom of information has led to “concentrated costs and dispersed benefits”. Politicians can very easily see the financial costs, but also the political costs. It's much more difficult for them to see the more long-term or more difficult-to-measure benefits, such as transparency. So there's a danger that you can actually see the costs much more easily than you can see the benefits, as it were. In a sense, the negative effects depend on from which viewpoint you're looking at it.
One of the often-repeated negative effects of FOI is that it actually leads to a change in how records are kept. It leads to the so-called “chilling effect”, which means either information isn't written down, or when it is written down it's written down in a very anodyne form. We found that how records have changed is due to so many other factors, that actually FOI has very little influence on this. So one of the significant negative effects we found didn't actually take place, although that didn't stop the Prime Minister, Tony Blair, from mentioning this in his autobiography.