If that single paragraph (or the first 250 characters of the article or whatever) is more than 30% of the entire article, then there is definitely a problem. But what if it's around 1% or at least under 25% of the article in total? That would fit the definition of "fair use" under copyright law, wouldn't it?
"...comment, criticism, news reporting, research, scholarship and teaching, with several factors considered, including how much material is involved as a percentage of the entire work and whether use is of a commercial nature or strictly for nonprofit, educational purposes."
Regarding caching: if that's brought into the copyright picture, then any web browser that uses local caching where it improves the perception of the value of the browsing software might be running into a sticky area, too.
The US government (anyway) has long defended "time shifting". It would probably be covered under the same laws that cover the legality of taping at TV show and watching it later.