Being rate-limited by LinkedIn isn't a contemporary analog to being extorted by force. You're choosing to use their service. You can choose to not use it.
The closest contemporary analog to being extorted by force is, of course, our relationship to our governments.
One of the most interesting aspects of libertarian thought is their notion that the liberal revolution (which began in 1776 and spread to Europe in 1789) is not, as we are inclined to think, complete. They argue that it is still in its infancy, and in some ways has regressed. This becomes clear when you consider the number of ways in which our modern governments are similar to those states (some feudal) which existed prior to the onset of the liberal revolution. You can now leave your lord's land without permission... but only if some other lord gives you permission to enter theirs. Our lords take far more of our incomes than was taken in the past (even under feudalism), and just as in the days of old, our lords dole that money out in a way which is best suited to their retention of power. If your entire village (or entire region!) doesn't support the elected lord, and endeavors to create a state of your own with a new lord (perhaps because you have been influenced by dangerous ideas like "[sometimes] it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature's God entitle them") then your lord reserves the right to reestablish the "consent of the governed" by force of arms! The primary difference is that they had no say in who their lord would be, whereas you decide (or, you are at best 120,000,000th of the decider) who yours is (so long as they come from one of the two established factions, of course).
When put in the appropriate context, the use of the term feudalism to refer to LinkedIn seems rather a stretch.