I have. A group of four of us (two buddy pairs) were diving a canyon that has a max depth of over 200 ft. We did sit down and make a dive plan, and decided on a max depth of 90 ft for our first dive. We descended to about 80 and the group stopped. One individual signaled to go down more, and everyone else gave him the level off signal. Despite that, he started descending. I signaled to follow, the three of us went after him, caught up to him at about 110 ft, stopped him, and insistently showed him our depth gauges and signaled up. He kept shaking his head and signaling down, and started descending without us, again. This time we weren't going after him. The rest of us aborted the dive.
The guy turned out ok. He told us (and his dive computer confirmed) that he did a bounce dive to 200 ft (on air). He wasn't narced and this had been his original plan all along (he does this particular dive site with other buddies and apparently this isn't his first time diving that kind of profile), which he didn't inform us of, and had even agreed to our dive plan, thinking we'd just follow him when the time came and he said he wanted to descend further.
None of us LIKED leaving him or wanted to do it, but there was no way, short of physically stopping him that we could've prevented his leaving us. And no one was about to follow him, with no plan or any idea what he was going to do.