Don't know about the BL in general, but a common thread I see in BL scripts by non-established writers is an irresistible story/logline. Whether it's in a positive way ("That's brilliant! I wonder how it ends...") or a negative way ("Really? They're gonna make a movie about that?"), these scripts have story concepts that provoke a strong reaction upon hearing them. Which makes even a jaded jerk like me kinda want to see them, if only to be an informed complainer. I have to say, script-reader blogs like ScriptShadow frequently cast doubt on the execution of many/most of these "breakthrough" BL scripts (at least the ones outside of the top 10 or so). But the story ideas always seem to be very hook-y.

A common factor? You mean OTHER than profanity in the title? (i.e. "I Want to F*** Your Sister.") I'm with Joe on the story/logline being irresistible. There's definitely a big percentage of high concept scripts. But then, that and the profane titles make a certain amount of sense - to get voted onto the Black List, a script must be memorable enough to stand out from the pack. A solid hook and a profane title are likely to be recalled many months later over a mundane hook and a bland title like "Love in the Afternoon."

TBSR: You mean "F***ing Love in the F***ing Afternoon," don't you?