I'm not taking a shot here. I find this all interesting and educational. In particular I am interested about the topic of potential for power, especially surge power, to crossover from the mains to the output of the adapter. Here is why I am most curious.
Having spent over 25 years in computers (field service) with a basic 2 year electronics degree, I had never heard the term "Crossover Limit" until I travelled to Tokyo about 7 years ago. Anyone familiar with this area of the globe should realize, among other things, the people in Japan are real sticklers for certain types of fine details. This knack is one of the reasons why they can build & maintain a city with a daytime population that borders on close to 3 times that of NYC, across a land area mass roughly the size of a postage stamp. (that was intended to be funny. Tokyo has lots of people, but little space, so they need to be good with engineering the most efficient use of their space. They are quite good at this. They are especially good at engineerin and buildings things up. They can't build out; they don't have much out. So they go up. I marvelled at this while there. Don't believe me? Go to Tokyo and see for yourself. I had a great time there. Nice people!)
Since I was in Tokyo expressly for the purpose of giving some technical training on a range of products that I/we supported, I soon was asked all kinds of technical questions. One of these centered on the issue of Crossover Voltage. I may not be remembering this correctly, but it sticks in my mind that at least in Tokyo, this is either also referred to as Withstand Voltage, or is somewhat similar in nature. The jist of it as I got it was, they were wanting to know the Withstand Voltage and or Crossover Limite for dozens of power adpaters used to power all kinds of different models of networking gear manufacturered in the states BUT that included a univesal power adpater. It was only during the process of this Q & A session that I learned for the first time that there is a potential hazzard for mains AC (especially due to transient fluctuations) to feed over to the output side of power adapters and potentially be a risk. From what I've since learned, I'm with AK, there seems to be some risk involved, but the level of risk is generally thought to be minimal.
That's all I got. Pardon the interruption. Please resume the educating dialogue :)