The topic of Google throttling traffic to a web site has been around since 2008 or earlier, at least we first discussed it in 2008.
Google throttling traffic means that they would only give your web site X amount of visits per day before flipping the results so another site can also get a traffic. It is like sharing the wealth in terms of Google visits.
Most SEOs I know of find the concept to be completely ludicrous. But there are many SEOs that believe Google does do throttling.
Truth is, it is probably a lot of factors that might appear to seem Google is throttling your traffic. Such as ranking changes throughout the day, news, searcher behavior, etc.
In any event, there is a thread at WebmasterWorld with a large discussion around Google throttling traffic in 2016. Might be a fun read if your day is slow today.
Forum discussion at WebmasterWorld.
Update: See my next story, Google: We Have No Web Site Page Quota & Do Not Throttle Traffic.
