I think there is a functional correlation between the two... the serpentine posture of Darlingtonia comes from the simplicity and mechanical resilience of helical forms, which is also ubiquitous in the ergonomics of snakes (climbing, striking - even writhing is a three-dimensional helix on a 2D plane over time.)
As for the tongue, that's probably largely coincidence. Forked things are easy to make with growth meristems, and an accessible way of increasing surface area of filamentous, low-volume structures. It just happens that both the snake's tongue and the "tongue" of the Darlingtonia have functions where surface area is a desirable feature; for snakes, it gives a greater sampling area for their olfactory receptors, and for Darlingtonia it diffuses more of the plant's luring scent and provides a larger landing area for flying prey. The tongues and similar protrusions of certain Nepenthes likely have a totally different function - that is, making an area of extremely narrow, poor footing which is both directly above the pitfall and is separated from safer regions of the pitcher by a single, easily blocked path. As far as I've observed, these tongues are usually heavily baited so that prey concentrate on them; the combination of a precarious position and crowding makes capturing insects much more reliable.
Evolution doesn't require the Darlingtonia to be able to see snakes, because evolutionary processes don't need to know in advance what the utility of a certain adaptation is. Have you ever heard of the "guess-and-check" method in your math class? Basically, evolution picks new forms more or less randomly based on simple variations of the parent form, and then relies on the virtues and pitfalls of the new forms to weed the bad ones out. The ancestors of Darlingtonia stumbled onto that shape because it was easy to find by chance from wherever they were before, and then the offspring that looked like snakes did a good job at reproducing. They didn't "see" that a snake-like form was worthwhile - if anything, they experienced it directly when they sprouted and grew snake-shaped leaves.
I think they chose cobra for the name since the "head" of the Darlingtonia doesn't have the typical flattened, wedge shape of most snakes. From the front, it has a silhouette reminiscent of a hooded cobra. Or maybe the person that coined the name just didn't know of many types of snakes, and cobra was just the word that sounded good.
~Joe
PS - Re: the evolution vs. creationism debate, I also think it belongs in another thread - probably another forum. Halt's original inquiry assumes that evolution was the mechanism which caused the correlation between snakes and Darlingtonia. The question isn't about the merits of evolution, just why this particular case worked out the way it did, given an evolutionary process.
PPS - Tipitwitchet is another, somewhat archaic name for VFTs, because the leaves "twitch" when stimulated.
PPPS - That got long!
PPPPS - Interactive demonstrations!
Biomorphs, a simulation originally created by Richard Dawkins.