The question is as per the title.
What Query Shark Says
Let's take a look at what precisely QS has written there:
This is a log line. Avoid them.
Think about it: it
[refers to: they must decide whether to resign their lives to inertia or fight for uncertain freedom]is a false choice. If they resign their lives to inertia, there's no story.
And worse, this kind of log line doesn't entice me to read on. Again, the goal of a query letter is to entice the reader to want more.
Log lines are imported from Hollywood, and they have NO place in query letters.
She's also written:
Here's the trouble with log lines: they undercut any kind of buildup to a punch line - they destroy tension and suspense. Consider how much more a reveal it is if that log line appears AFTER these next paragraphs.
Honestly I think log lines don't serve a writer well. You have an entire page to work with here, don't try to condense it to a single sentence.
This sentence doesn't actually say anything. It uses metaphors that don't apply to anything in the book (cards), introduces a character not in the query (a killer) and tries to set up tension...there's no tension in flabby sentences.
What Query Shark Means
I'm not sure my answer corresponds with QS's opinion precisely, but here's what I'd take away from what she's saying. Writers tend, in log lines, to try to amp up the drama tremendously, while not being able to provide any meaningful detail. Very often, the result is artificial (hence she's able to easily, intuitively, pick them apart and expose how hollow they are), and also not compelling (because of the lack of detail - which is what the agent/editor is actually interested in - and the familiarity of the format; it probably comes across at best as exciting hyperbole with little focus).
The log line may be effective for marketing purposes, when it's aimed at a less-discerning audience who aren't committed yet to devoting any attention to this particular piece. In a query, though, you've already got the agent's full attention; what they want to hear is detail about the book. A log line usually doesn't supply that, and some agents may find them actively irksome. They also have a tendency to be poorly constructed or thought out, which adds to the nuisance. Hence (I presume), Query Shark does not like log lines in her queries.
Log lines are just a way of quickly, pithily summarizing your book's plot and appeal into one sentence.
They're not necessarily bad. as the Query Shark admits, lots of agents recommend using them. They're a style, and as such, some will appreciate them more than others.
I think the thing to definitely avoid is using a BAD log line. Make sure you actually say something important in it, and don't get so caught up in being pithy that you make the content nonsensical. In the Query Shark's example, everyone knows that the characters of the book don't "resign themselves to inertia" so those are really wasted words, even though they have a nice ring to them.
As stated a log line is used more in the film industry. It is a quick "statement" with a beginning, middle, and end that summarizes the story. Typically, a sentence or two.
In the publishing field you send a query letter with a pitch.
The pitch (like it or not) should include your introduction, a summary of your work, your credentials, and your closing.
The summary is 100 to 200 words that presents your setting, your protagonist and the problem.
I will suggest that the intro,credentials, and closing are close to the same length together as the summary (200 words.) You are selling yourself with these. The summary sells your story.
So you have 400 words instead of a couple of sentences in a log line. But those 400 words have to all be golden and convince an agent/editor they want to read more. Those words are the only chance you get to make a sale.