Planet13 - 8:03 am on Aug 1, 2011 (gmt 0)
Regarding the two sets of keyword phrases in a double size meta description, I think that would look a bit unnatural and neglects to focus on the most important function of a meta tag, which is to promote a clickthrough.
I think you are referring to the SharkSeo example I posted.
I think the key was to max out each sentence at (or near to) the limits that google displays. So if google normally displays 156 characters in the description field, then there would be two sentences nearing 156 characters per sentence.
Then say the two most used entrance keywords are "widgets" and "foobars". One sentence would focus on widgets. The other sentence would focus on foobars.
So if the user searched for widgets, in the snippet area, google would display the sentence in the meta description that related to widgets (but NOT any of the sentence that is related to foobars).
If on the other hand, the searcher had used foobars as their keyword, google would select the second sentence (which was about foobars) to display in the rich snippets (and would NOT show any of the first sentence, which is related to widgets).
I guess the important thing is that each sentence has to be near the max number of characters allowed. Also, we have to keep in mind that google might show ANYTHING in the title or snippets, so who knows what will appear?