Facebook links used to be so bad with this until they changed something in the built-in browser to catch them. Now every time I get a "this page is trying to leave the app" confirmation box I feel extremely satisfied that the redirect was squashed.
I thought Safari doesn't even allow this anymore because of all the popup forwarder spam?
I still experience it every so often (iOS 8.4.1). The last time it happened it was on Techcrunch
I see. Looks like they were at least to be blocked, but the system either wasn't shipped or doesn't work reliably.
UIWebView is definitely still vulnerable, as I've seen it when browsing sites through the default Twitter iOS client. Not as frequently as in the past, however.