I was watching a 2014 episode of 'Shark Tank', Season 6, Episode 3. A woman pitching 'HeartPUP', a pet carrier, said that while in law school, one of her professors said, "Patent laws are changing next month, if you put this on the internet now, you'll have a common law patent..." And then she was interrupted. Was this something legitimate? Is there such a thing as a 'common law patent'? I can't find anything online that refers to it.
There may be common law trademarks, but patents are a grant of a time-limited monopoly from a government. A fairly radical U.S. patent law (in my opinion) was signed in 2012 with various aspects going into effect over the next 18 months or so.
Under the new law one can publish the details of an invention and then get a year to actually file. If followed up on within the year, the publication would effectively be part of a first-to-file system providing protection - if and when a patent issued. Under the old law someone else could establish that they invented it first regardless of your publication. Under the new law, if they file the day after your publication they would be denied as being old - period.
Of course the day it was published on the internet all possibility of any patents outside the U.S. would be gone.