The last couple editions of D&D (including Pathfinder) have had some pretty heft Updates and changes over the years.

Updates a not a new thing, but they’re much more visible now. Dragon magazine used to be the place for errata, making them invisible for no subscribers and those who discovered the game after that vital issue vanished from shelves. The errata for Unearthed Arcana is reputed to have been particularly useful.

With the Internet and the ease of being able to revise the game after its release, errata and Updates became more common. Many of the Updates were needed, fixing powers and abilities that were often so disgustingly broke, they probably never should have seen print. At the height of the revisions, when the updates were at their worst, I was telling my players not to use the latest book for a month until the first wave of Updates had passed and cleared away the most broken options.

Even after I migrated from 4th Edition to Pathfinder, a different party managed to break a boss fight through a poorly worded spell, sending me to the Paizo forums that night, scrolling and hunting for a clarification or Designer’s corrective post before the next game.