A movie is a movie. I think we're all getting way too nitpicky with what is and isn't "a movie" when I have an incredibly strong feeling that we all know a movie when we see it (the "you know sci-fi when you see it" method has been applied to great success at SF&F). Would anyone honestly, HONESTLY, call "The Wire" a movie? Would anyone? Who would ever call "I Love Lucy" or "Hannah Montana" a movie? Those are unquestionably TV shows. Does anyone leave a screening and say "That Coca-Cola movie before the Muppets movie was a really great movie!" No. Because we know it's a commercial. It's shown in a theater like a movie, it advertises products like a movie, and is intended to be shown in a theater like a movie. But it's a commercial. And no one would call a commercial shown in a theater a movie, and no one would ask a question about it on this site. And if they did, you close it, because it's obvious that it's not a movie.
For the most part, and this is true for almost every question on the site currently, a movie is a moving picture of at least 60 minutes in length that as originally shown in movie theaters. Are movies sometimes shorter than that? Sometimes incredibly shorter. Were they originally released on DVD or shown on television? Sometimes. Yes. And those are on-topic here. But giving a hard definition of what movies are (when we all already know what a movie is 90% of the time) we will end up including EVERYTHING and therefore losing the real scope of the site. If the people lobbying so hard for a definition of a movie could come up with a definition of movies that includes movies and television (since there's such a support for TV to be covered here) WHILE somehow excluding music videos and commercials, go for it. I'd like to read that.
The instances where there will be weird vague overlap are going to be so few and far between. Do we honestly expect a ton of traffic about a Hallmark Channel movie? Or "Holiday in Handcuffs" starring Melissa Joan Hart and Mario Lopez? When TV movies and miniseries come up, on the off chance they do, deal with them on a question-by-question basis. The criteria set forth in the name of this site, "Movies," is incredibly clear.
We are attracting smart, literate, well-educated and critically thinking people to this site. If someone honestly thinks that the dancing popcorn box they saw before "Tinker, Tailor, Soldier, Spy" is a movie in its own right, they need to be corrected.