Depending on the source I just use a paragraph or so. If its a short article then a sentence may be more appropriate. I find the whole thing silly. I can buy a whole newspaper, with full articles and leave it at a restaurant for some other customer without cutting away 3/4 of each article. How is that any different than posting an article, that includes a link, to the originating site and author? And why don’t they go after people that send articles in email?? You’d think they would be glad that someone is reading their material and encouraging others to do so. Why it may even help drum up business for hard copies.
Agreed - it’s a bit like buying a book and not letting anyone else read it!
My understanding of US copyright law, which I have to work with most days, is that excerpts of no more than 5% of the total article are considered fair use for commentary, with proper credit and without selectively and creatively excerpting so as to put the copyright holder in bad repute.
I prefer to err on the side of caution, as fair use is always a judgement call and, since it is a good chunk of my livelihood now, I’d rather not spend everything on attorneys!