Yup. I've gone entire portions of a straight pool run using just an open bridge, or just a closed bridge, or flip-flop between styles (because of a hurt finger or what-not), and not even know, until someone -- a "bridge zealot" (which I'll mention later) -- pointed it out to me. They'll ask, "why did you shoot that series of shots using nothing but open bridge, and then suddenly you switched to closed bridge?" My answer is at first an honest "I don't know," followed by a, "probably because the shot dictated it for ball-/rail-obstruction or draw or follow or comfortability reasons."
It might be helpful to realize that there are different styles of closed bridge, as well. While the "index finger looping over and contacting the thumb" seems to be the "classic" picture folks get in their minds when they picture the closed bridge, there are others -- and ones which are now more popular than that style, due to being more conducive to stability and accuracy.
The mislabeled "Filipino bridge" -- where the index finger presses down upon the top of the middle finger -- is almost a de-facto "must know" in the higher echelon of play. This type of bridge creates a "V"-channel inside that the cue shaft is guided on, which is much more accurate than the meaty loop offered by the classic "index finger looped over the shaft and touching the thumb" style. However, there's a trick to orienting that internal "V"-channel vertically so that it offers the same side-to-side stability that an open bridge offers:
http://forums.azbilliards.com/showthread.php?p=3119239#post3119239
And, one of the most unique closed bridges occurs when you take either of the above two types -- the "looped index finger" and/or the "index finger pressing down upon the middle finger" bridges -- and you fold the top half (last two joints) of the middle finger under the hand. In other words, only the upper segment of the middle finger is visible and supporting the cue shaft; the rest of that middle finger is folded under.
Willie Hoppe demonstrates:
http://youtube.com/watch?v=sc4iaJWu8Ak#t=2m38s
What this does is to offer even more stability, and, in the case of the index-pressing-down-upon-the-middle finger bridge type, a naturally vertical "V"-channel without lifting the palm of the hand in the air nor any need for "scrunching." I use this for power draw shots, because folding that middle finger under the hand lowers the bridge close to the table surface, and because of its stability, you can really
crank on the draw shots with little fear of miscuing, because the apex of the "V"-channel itself is resting on the table surface.
Summary: it's helpful to learn multiple bridge types, not just "open or closed." I see far too many people who choose one side or the other, as if it's an "either / or" contest, and count how many times they use either type, without really understanding why or what purpose each particular bridge type serves. (Or even worse, you get the "bridge-type zealots" who advocate one style of bridge type "no matter what -- you're a noob otherwise.")
It's a more-tools-in-the-toolbag thing, is what it is,
-Sean