I missed this interesting post.
srtpal is correct. The standard practice for many syndication parties, is that reading speed should be around 140 words/min, with a strict maximum of 180 words/min. Even slower for children movies.
In some movies -and most of TV series-, it is not uncommon for spoken dialogs to be above 250 words/min. So the written caption has
to be shortened. Especially nowadays when distributors send timecode templates to professional translators, to have the subs translated into up to 50 different languages with various reading velocities. Also this prevents the subs to overlap the scene changes -which is considered bad practice.
A Verbatim sub is generally not professionally made; rather created by a fan who does not have the same care about children/deficient people reading speeds, or scene changes.
Also see this Wikipedia link for difference between subtitling and captioning http://en.wikipedia.org/wiki/Subtitle_%28captioning%29