The new LinkedIn and OkCupid apps are primarily HTML5 based. Not quite the same, but every new release of the Facebook app seems to have more of its existing views replaced by HTML5 counterparts.
Granted, there are other approaches you can take to get this behavior, but I'm not sure why you would. My impression is that they're using HTML5 in these areas.
I know that Facebook is very pro-HTML5 but I don't think there are any views in the native iPhone app that are not native UIKit or based on three20. I'll ask around, would be nice to now if there's any shared code at all on their end.
Check out the video at ~16 minute mark.
...but when I am it's by Joe Hewitt. TGIF!
Basically, they reuse cells like UITableView does.
http://cdn-0.nflximg.com/us/presentations/htmltvui/oscon-201...