The tag fixme on OpenStreetMap is used to “mark objects [...] that need further attention“. Using the XAPI, I’ve downloaded both nodes and ways within the bounding box -0.05, 52.03, 0.22, 52.25 which are tagged with the key fixme. When the two XML files are loaded into JOSM, they produce an unsightly picture of how much quality assurance work needs to be done. Below is an example of what I mean; the data being displayed in the screenshot is from 26th December 2010.
Busy-looking, eh? Just to bring this back to reality somewhat, here’s a similar screenshot with the outline of Cambridge superimposed:
If you are familiar with editing OpenStreetMap and live in the south Cambs area, this anchor will take you to Keep Right: an awesome “data consistency check[er]” for OpenStreetMap—just check the “fixme-tagged items” checkbox on the left. Each purple lightning bolt is a request for investigation.