My understanding is that there are very few cannabinoid receptors in the central nervous system, so it really is pretty much impossible to "overdose" in the opiate/barbituate sense.

If by "overdose" you mean take enough to have an extremely unpleasant experience where you THINK you're dying, yes, you CAN do that, & the usual culprit is edibles.

The vast bulk of my consumption is oral (tincture) & I've never gotten "too stoned." I've been where I could see "too stoned" pretty clearly, though - yep, there it is, right over there...