There's been a lot of controversy about spoilers in Doctor Who fandom recently. Spoilers have always been a topic for debate among fans, but Steven Moffat's impossible time loopy type of storytelling seems to have raised the stakes and brought the issue to a boil.
There are a lot of different opinions on what constitutes a spoiler. There's even a newly resurrected term going around, "Teasers". Teasers seem to be basically spoilers, but with a critical bit of information withheld. (One of these four characters will die!)
There's also a lot of disagreement about the source of the information mitigating the spoilerishness of the spoiler. Some people believe that any information released by the BBC or by Doctor Who Magazine can not be considered a spoiler, but there seems to be just as many people who disagree.
For instance, When I watched The Impossible Astronaut, there was a scene where an "astronaut" comes out of a lake and the Doctor turns to his companions and says, "Whatever happens here, do not interfere.".
This scene was intended to be quite surprising, the audience is meant to be experiencing certain specific thoughts, specific questions posed by the author. Instead of experiencing what the author intended, I was thinking "Here comes the scene where the Doctor dies.".
While watching this scene my wife gasped, I did not.
The knowledge I gained from the cover of a recent Doctor Who Magazine, altered the viewing experience intended by the author. -but did it "spoil" it?
This is largely a matter of opinion. I certainly enjoyed the episode and found it highly entertaining. Would I have enjoyed it more without that knowledge? Yes, actually I would have, but only a little.
Spoilers aren't a black and white thing, there's a large grey area where fandom can not reach a consensus. The same information that "spoiled" my experience also tantalized casual viewers, driving up viewing figures and helping assure Doctor Who's continued production. (or so the theory goes.)
I think Doctor Who fandom can cope with the spoiler debacle, or at least debate the issue intelligently, but like in any rational debate it's necessary to define the terminology. This hasn't really happened yet in the fan-lexicon concerning spoilers.
That's why I'd like to propose a system to quantify spoilers into definable terms.
It won't be a perfect system and it definitely won't please every one, but maybe it'll be a step in the right direction.
The Spoilcon System
Modeled on the United States Armed Forces Defense Readiness Condition system, DEFCON, this system categorizes information about upcoming episodes of Doctor Who into five graduated categories based on it's potential for spoiling the viewing experience.
The Spoilcon system does not take the source of the information into consideration, nor how widely known the information is thought to be, it only considers the information itself.
Spoilcon Zero: (Not a spoiler)
Any information from a "Next Time" trailer, Episode titles, air date, length of episode, whether or not it's a two-parter, or any other information that the viewer is usually likely know beforehand in the television format.
*If an episode title gives too much away, that's bad writing/producing, not a spoiler.
Episode location/setting, unless that setting is a returning setting or one with special significance.
Casting, unless the actor has previously appeared.
General episode type description. (a historical, a romp, continuity heavy, Doctor light episode, etc.)
Returning settings, unless that setting has special plot significance.
General episode plot descriptions, unless involving a returning villain (Children are disappearing in ancient Persia. The Doctor races to stop the mysterious Semerkhet before he awakens an ancient evil.)
Casting of returning actors, unless having played a character with special significance.
Returning villains, unless arch enemies.
Returning arch enemies, or the casting of actors who have played arch enemies.
Returning characters who supposedly died, or otherwise supposed to never appear again.
Returning locations/setting with special plot significance. (Gallifrey, Mondas, etc.)
Specific plot details.
Appearances of past incarnations of the Doctor.
Well, it's not perfect, but it can be improved.
Let me know what you think.