Sounds like a lot of new personal TB's being launched and dipped in previously-visited caches. A personal TB is not at all uncommon. I was 100 in when I started my personal TB and WAY too lazy to go back and put it in all 100, but many people will.
It's a shame there isn't a more elegant way to handle personal TB logging -- not just catching one up, but the hassle of logging it in and out on an ongoing basis -- but I could never think of one, so I haven't made any suggestions to that effect.
I think they should add a "dip personal TB for milage" button on the cache page.