TomTom makes its money from navigation solutions, so it's not a huge surprise that it's not terribly fond of open source maps on a general level. It has been accused, however, of overstating the error potential in competing open source map sources as part of a blog post discrediting them. A post on TomTom's site highlights the problem from TomTom's point of view:
"In one particular instance, a leading open source map was compared against a professional TomTom map, and shown to have a third less residential road coverage and 16% less basic map attributes such as street names. Worse still, it blended pedestrian and car map geometry, and included ‘a high number of fields and forest trails’ classified as roads. Indeed the major benefit – the community aspect – has itself presented problems, leaving maps wide open to attack. A highly-publicised case saw a leading provider suffer over 100,000 individual attacks, including reversals of the recorded directions on one-way streets."
"Many drivers rely heavily on satellite navigation for precise directions, and mapping errors can be extremely dangerous, particularly in the case of one-way streets."
The open source mapping community isn't taking this particular challenge lying down, however. Slashgear reports that the open source community isn't happy, with one blogger taking particular exception to the number of claimed attacks, stating that:
"no more than a couple of dozen were - and those were swiftly spotted, and fixed, by the OSM community."
GPS map data in Australia associated with commercial GPS products typically comes from one of two mapping sources -- Navteq or Sensis -- and there have been some notable gaps in maps that I've spotted for years. It wouldn't shock me if open source maps were less complete than paid ones on the basis that one relies on free user input, but equally, is TomTom backing itself into a rather obvious corner when it comes to attacking the accuracy of map data? [TomTom via Slashgear]