It's just an ad lib on the topic title from the link posted
Mt.Gox CEO Karpeles says bitcoin exchange is at 'turning point'
Simply put this is a turning point what type it will be is what makes it interesting
If you meant the definition of the term it means when something significant is about to happen that changes everything
Example the change from candles to kerosene to gasoline power were turning points
The Eternal September when a significant amount of users were introduced to the thing called the internet is a turning point
In more modern terms the rise of social media giants like facebook and twitter may be turning points in how we talk to one another and are a part of the greater worldwide communication system.
Possibly even the recent revelations that PRISM gave the public and the Constant campaigns for copyright law vs public use could become turning points for privacy and free and open access to information, for all people not just those that can afford it.
Basically a tipping point is something that brings about a significant change, whether that change is for the better or for the worse is another discussion however it does lead us somewhere important into the future.
What Gox did is raise the question of if their is a such thing as too big to fail in the Bitcoin world
Whether Bailouts are even possible and if the lack of financial instruments may be a strong point or a weakness.
Will it result in stronger exchanges, will exchanges become more decentralized than centralized and what will come from this lesson as people realize this, what are the implications it could have to finance and how we handle these type of issues with a limited supply, as these type of questions are digested and interpreted upon it becomes worth asking and considering what the answer to these problems are and one that I look forward to seeing solutions being created for in the future.