Here is an interesting article about a recent lawsuit 3M filed and lost, regarding its famous Post-it Notes patent. What's interesting about it is not the verdict (at least for this particular blog), but the covenant not to sue that 3M had agreed to in 1987, and the basis for it:
3M had promised not to sue Barton Nelson back in 1987. As long as Barton Nelson didn't change the way it put adhesive on custom-printed, semi-sticky promotional products, 3M wouldn't ask a court to decide whether Barton Nelson's products violated 3M's Post-it Note patent.
Both companies' notes can be easily unstuck from an adding machine or typewriter and restuck to a file folder, but each creates the "repositional" effect by a different method.
3M's adhesive contains microspheres that prevent Post-it Notes from sticking too firmly to a surface. Barton Nelson created its adhesive, CFO Bart Nelson said, and applies it in small globs with a textured roller.
"It was an aggressive adhesive, but the small-spaced dots and islands made it repositional," Nelson said.