That coment is the only thing I've seen suggesting that Tomtom fired first. I find it very hard to believe (having contracted once for TomTom a few years ago and found them a very sound outfit, with really good technical people still at board level). Groklaw seems more likely to be right than random slashdot comments: http://www.groklaw.net/article.php?story=20090320000835463
Posted Sep 24, 2009 15:33 UTC (Thu) by epa (subscriber, #39769)
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I didn't see anything in that Groklaw article saying that Microsoft's lawsuit wasn't in response to a patent threat from TomTom. (Not that it is Groklaw's job to refute every random theory floating around, but I don't see how the article you linked to is relevant here.)
You are most likely right about TomTom as a company; I knew they had fought Garmin in court but it appears that was defensive (see here for example).