I do anchor regularly, and my boat has only seen a mooring ball one time. While I have never dragged I have had "failure to set" on occasion. My first anchoring challenge was in my sailboat. We were anchoring in a small cove only protected by a reef from the Pacific Ocean. There was another sailboat anchored already and this was my first anchoring experience. We entered intending to put out two anchors like the first boat. I threw a stern hook off near the beach and headed out towards the reef. Dropped the main and pulled back and set. I looked at the boat next to me and they were shaking their heads "NO". Sure enough I started drifting too close. So, I pulled it all up, went around again and this time dropped the main first then the stern. I got settled and looked the the boat again. They were shaking their heads "NO". I began drifting into the cliffs to starboard. I pulled everything up again, went back the the first plan, adjusted my location, dropped the stern then the main, got set and the other boat gave me the thumbs up. Then I put on mask snorkel and fins and went to look at my anchor. It was a Danforth and while it felt solid on the boat, it had only its points grabbing a crack in a large flat rock. So I was able to get slack and swim it out to sand and set it by hand. Whew.
So my buddy has the same boat, new to him. We looked at marking the depths on his chain and the method I told him about from this forum was to weave colored line in the chain. He bought the line but it was going to take so long to go through the 420' of chain he decided to paint. Well the problem came that he took a group out to Catalina Island for the 4th and couldn't get a mooring ball. So he tried to anchor but he didn't really know how much chain he was putting out. So, now the group was at dinner and the Coast Guard calls him, "Sir are you the captain of the ">>>>" Your boat is adrift. Holey crap. Luckily he was drifting out to sea rather into anyone else. Oh boy.