Comment 10 for bug 1264795

Unfortunately, this functionality is provided directly by Unity without any configuration option. If you're not using Unity, let me know but it's the only reasonable explanation that fits the data at this point.

If the problem is stray capacitive discharge in the device itself, you don't need to touch it. It doesn't show up in other applications because it requires a particular sequence that gets interpreted as three separate simultaneous touchpoints followed by three more separate simultaneous touchpoints, and that sort of thing could happen easily if the dielectric in the touchpad has a thin spot or is misaligned on one edge. Few applications look for that sequence of events, if any, and it's likely that hardware QA processes also don't check for such a thing.

Really, adding a new configuration option to disable 3-touch application switching is the simplest solution.