When you have to turn to Google Trends to try to support your point, it's a pretty flimsy point. If we believed your data, then 2012 would be the high water mark for Facebook usage (globally), which is obviously false when you look at actual user numbers released by Facebook. A much better explanation for the decline in searches is the shift to mobile, where people actually have the app installed and hence don't search to find the website.

The VentureBeat article is obviously anecdotal and relying on poor data.

Doom and gloom all you want, but the only real numbers we have (from Facebook) directly contradict your view. If you're trying to force the data to fit your hypothesis, it's usually a sign that your hypothesis is wrong.