Banner Ads on bottom of different apps- Is this a Virus?
There are various advertising networks that will use cookies and the likes of which to track you and profile your online movement, and then later use those to target ads at you. It is possible that the NBC and Huffington Post Apps are using the same avertising network and thus showing the same/similar adverts.

You might want to check out adblockplus for android, it no longer requires root access and their installation instructions are quite easy to follow.