Drying by leaving in the dark..

Suppose you left a plant in the dark after it had ripened etc.. but didnt harvest it.. just let it dry and die slowly.. would that make for a really nice potent smoke or what?
doesn't darkness increase thc or osmething?

I wouldn't just leave it without harvesting, a buddy of mine did that and it ending up tasting like crap compared to the rest which he did harvest.

Don't just leave it unharvested. The root system will still suck up water, even if the plant is dead, so the buds will still have a water supply, thus the drying process is severely slowed down, offering major chance to bud rot to settle. Plus, if there are still nutes in the soil (and there ALWAYS are) the root system will still take it up, sending it streight to the buds, causing some nasty taste.

Darkness does maintain THC concentrations. Light usually accelerates the change of THC into CBL, a cannabinoid with no psychoactive effect.