Interesting. From the statistics I can see, the team seemed to regularly return about 300,000 points a day until the 18th when that dropped by about a third. Four days later, that remainder dropped by two thirds. Yet if you look at the team by points, it shows only 16 members with one of those retired. One member, scubadoo, has 103,537,296 points while the team has 104,751,029. I don't see anything that would explain the drop off in points but with one member having such a high portion of the team's points, any change for them could show up as equally dramatic for the team. I do see that that one use is still returning results but I can't see if they've dropped off. I suspect though that your answer lies there.

I think you'll find more often that not, people don't retire from a team when they stop crunching. A general rule of thumb is that on any team, only about one third of its members are actually actively returning results.

As for what happened to that one member of the team, there are any number of possibilities. They may have stopped crunching and the team total dropped by a third while their Pending Validation results awaited validation (assumes they used BOINC, not UD) and then dropped again after that. Then again, if that user is still returning results, they simply could have lost access to a number of machines that they had been crunching on. It could be that the user is off on holiday somewhere and powered down their machines while they're gone. There's plenty more of quite reasonable explanations too.