One of the reasons people want web writing to be short and to the point is because reading on a computer screen is more difficult than reading a physical copy. It causes more strain on the eyes and the average person has a hard time staying interested for extended periods of time.
The most important aspect of writing on the web, and really any type of writing or journalism, is to make sure you don’t bury the lead. Get the most important information out at the very beginning of whatever you are writing. Once you get that information taken care of it’s a good idea to include pictures with captions, embedded videos or links to other websites with more information. The goal is to keep the reader as interested as possible by having them interact with your writing.
I think the best examples of this are blogs like the Huffington Post. This article on George Clooney’s donation to President Obama’s campaign demonstrates several effective techniques. The article includes a video of Clooney and Obama together, links to other articles on the subject and an embedded video on Obama’s most recent statement supporting gay marriage.
As far as longer reads that keep people reading I think a lot of it depends on the way the text is broken down. For example, former NBA great and current NBA/NCAA commentator, Steve Kerr wrote an article for Grantland.com about why the age limit to enter the NBA needs to be raised to 20-years-old. People were interested in this because it’s a hot topic coming off of Kentucky’s national championship of mainly one and done players. He does a nice job of breaking the paper down into five numbered sections. Kerr also uses a bulleted listed to compare NBA players who benefited from staying in college and the few exceptions of NBA players who have made a significant impact out of high school.