From time to time, the government issues temporary flight restrictions, or TFRs, which pilots are responsible for knowing and following. In the west we get a lot of them in the summer months because of firefighting operations. When a tanker is coming in to drop fire retardant, they don't really want to worry about what other planes in the area might be doing. Other TFRs deal with sensitive national security areas, stadiums during games, and even the President's ranch. In the past when you wanted to know what current TFRs were in effect, you had to call the regional flight service center (run by the FAA) and get a briefing. Needless to say, that often doesn't get done.
Now, the BLM has a web site that lists TFRs by state and provides maps. This is a huge improvement and makes it much easier to visualize where not to fly. I wish it were designed a little differently to encourage use of the data by other programs and not just people. There are numerous web sites that pilots use to gather information and it would make things safer if all of the relevant data could be more closely integrated. Making data easy to use in multiple formats isn't much more costly than creating single-use data sources. Government's have a duty to make data as widely available as possible. I wish more eGovernment applications took that responsibility seriously.