I've seen a (large) number which just send you to the root page for the app (or company. or blog. or worse). Often without any clear way to send an email or report a problem, just a splash page that prompts you to download the app... which you've evidently downloaded.

Personally, a "report a problem" link would be a lot more inviting, especially if it let you send them a message from the app store, and include the last crash report (if it was the last one).