You could say the lawsuit was made in retaliation against Motorola's own lawsuit against Apple, in which Motorola claimed that Apple simply ignored Motorola's patents on several mobile technologies instead of licensing them when it developed and released the iPhone.
Technology companies like this often push the envelope when it comes to using technologies that might be patented by competitors, but since it happens so often, a sort of mutually assured destruction prevents things from flaring up. Unfortunately, the nuclear holocaust of lawsuits seems to have begun.
About a month ago, Microsoft sued Motorola over smartphone-related patents, too. And while we enjoy the multi-touch interface on the Droid, it's arguably ripped straight from the iPhone experience, and that technology is patented by Apple. Whether that patent will hold up in court remains to be seen.