Recently I've noticed a new trend in user interfaces. Facebook and Twitter do this, and I've come across it on other random, less famous sites. However, to keep things simple, I'll just use Facebook as an example.
When you first log into Facebook, you are presented with a "News Feed" that has a certain amount of posts from your friends. The feed extends down past the bottom of the viewport.
Then, when you scroll down, to see the feeds "below the fold", at some point as you move downward, it loads in more items. Apparently, this is called "infinite scrolling".
On my computer, this often causes my position in the feed to jump while I'm in the action of scrolling, which is really annoying.
What's particularly egregious about this UI concept is that there is footer information at the bottom of the page. I advertise on Facebook, and use the link at the bottom of the page to get to the advertisement management interface.
Because of this incremental load feature I'm describing, I often scroll down to the bottom to get to the link I want, when I reach the bottom of the page, it will suddenly load in new data, pushing the footer down again, and I have to scroll down again.
This whole thing seems completely pointless to me. What's the upside? A Facebook page is near a megabyte of data, so saving the few extra kilobytes of feed data for when the user scrolls down is just not worth it.
What's wrong with a link that just says "show more"?
Since this additional data retrieval thing seems to happen as soon as I start scrolling even a little anyway, why not just load that data in the first place?
To me this minor annoyance reeks of some engineers concept of a "neat trick" that does not have any actual appreciable upside.
Or am I wrong about that? Is there an advantage that I'm not seeing? Am I the only one who thinks it's stupid? Do some people like it?
The accepted UX terminology for this pattern is "infinite scrolling". It's becoming more and more common in rich web apps because it's a way to keep users engaged with a minimum number of roadblocks.
The accepted viewpoint is that users prefer single page versions of content when given the choice (Google's own research backs this up), but that it's impractical to load hundreds of items on an initial request (especially for a media-rich site like Facebook).
What's the problem with pagination? To quote UI-Patterns:
The problem with using pagination for browsing between subsets of data is that the user is pulled from the world of content to the world of navigation, as the user is required to click to the next page. The user is then no longer thinking about what they are reading, but about how to get more to read. This breaks the user’s train of thought and forces them to stop reading. Using pagination creates a natural pause that lets the user reevaluate if he or she wants to keep going on or leave the site, which they a lot of the time do.
Infinite scrolling is not right for all applications, though. The scrollbar continuity is a problem, as you identified, but there are other issues as well. Some of these can be addressed by adhering to a number of best practices, very well outlined by UX Movement.
Difficulty in bookmarking, and inability to jump to a specific result are other issues. That's why it's important that infinite scrolling only be used in data-rich applications, where the results displayed are highly dynamic (and will necessarily change from day-to-day, so bookmarking isn't expected to return specific content), and unpredictable (so the user would have no reason to "jump to page 7", since there's no way of knowing what's on page 7).
Overall, infinite scrolling can be a powerful tool, but only if implemented properly in the proper context.
