I’m really starting to hate the trend of apps having their own built in mechanism for browsing webpages.
Guilty parties on Android: Facebook, Twitter, Delicious, Reddit Is Fun, Feedly, and probably some others. Most have options to turn it off, but some don’t (I’m looking at you, Delicious).
Your app should do what it does, and when you click a link, open the default browser.
Opening within an apps limits a lot of things. What if I want to bookmark the site? What if I see a couple of links on the page I want to open, but I’m not done with the current page?
Operating systems have URL handlers for a reason. Use them.