Robert_Charlton - 9:05 pm on Jul 28, 2013 (gmt 0)
deeper - Great question. The answer probably varies according to the type of content you have.
For a teaser, I've assumed that a short focused overview paragraph... and/or series of short paragraphs set up as bullet points (on some types of sites) makes sense... and then you might go into subheadings. If you use bullet points in the teaser, and relate them well, these are probably most easily parsed if structured as an unordered list.
Conceivably, a contents section, with an unordered list of links which link to named anchors on a page (Wikipedia style) might constitute part of a teaser. I'd tend to use at least a short paragraph of text before that.
Not all content works as lists, and on many sites I avoid them entirely. The content itself might (or might not) follow a structured outline. Not all kinds of writing can be structured that tightly in advance, and pre-structuring can often be inhibiting to particular writers.
I feel that search engines, which are machines with limitations, will have a much easier time parsing content that is at least well constructed. Giving the engines extra clues, via appropriate markup, should help.