I find this news both surprising and not-so-surprising. Surprising in that they chose ForumRunner rather than Tapatalk. Surprising in that they wanted to actually acquire the team that does the mobile app for their gain.
It's not so surprising because, as Steven said, everyone has a price...
You really can't blame ForumRunner for their business decisions.
Everyone has a price. EVERYONE!
...However, IB gave ForumRunner an "offer they couldn't refuse."
ForumRunner is just a brand, the company that ran ForumRunner is End of Time Studios, LLC which more or less will be absorbed into vBulletin Solutions.
It is funny when comparing TapaTalk to ForumRunner most people prefer TapaTalk.
I have always liked ForumRunner better and installed both on my sites giving members a choice to what they preferred.
That just means that Tapatalk just got viral. It happens when a company acquires a well-known brand and the majority of the "other" side don't like said company. In this case, not everyone is happy about the announcement of FR being acquired by IB. This thread proves it.
The problem here is that a lot of people know Internet Brands as a company that buys brands and then drives well-known, highly regarded brands into the ground. That is an IB problem; their reputation more or less
hurts them.
It obvious they want it so they can eliminate addons for competitors and have a monopoly on the fully integrated suite with mobile.
A lot of companies do this. But you knew that.

In other cases, they acquire to absorb the talent behind the company/brand. Others do it to gain a much, much bigger marketshare.
I would assume IB have already tried to acquire Tapatalk and offer declined though that is all speculation but I would have imagined if Tapa are the bigger company they would have been contacted by internetbrands. Thankfully I don't use either and will wait for something official to surface whether it be free or paid.
How large a company is - irrelevant. Many large companies buy out small businesses.
A stock mobile skin will serve the need for a lot of XF sites but there will always be those who prefer an actual mobile app' that offers push notifications and deeper integration (such as uploading directly from the camera). If a dedicated mobile app' doesn't offer integration, is just serving as a front-end to the content, then I would be hard pressed to see why anybody would use it instead of the stock mobile skin.
As much it would be nice to use something like Tapatalk, I just want to avoid the headaches of crashing because the of the fact that the app is a modification done by another person, rather than the person building the app. In this case, I'd rather take the official skin from xenForo devs than Tapatalk. Even though that I know a lot of people like and love Tapatalk. It's pretty popular.
I see a lot of people talking about tapatalk, and asking for support for the app on other websites than here. A lot of people come into a vB3 forum and ask for Tapatalk. So, tapatalk has a really good team... That one of these days, they'll hit the jackpot. Right now, tapatalk is at a point where they're close to that jackpot. Very close.
Anyway, the point that I was making is that I know that Tapatalk is popular, but I would choose an officially marketed, and supported mobile solution rather than something from ForumRunner or Tapatalk.