In this month Yahoo changed some things at their portal and it effected some of us. I realize this when i check one of my dream Yahoo! ID and it said it is available . I don’t think the ID deleted / pruned cause i get junk emails everyday. When you create a new id no one knows it so they cant spam their junk.
Another one is when i try to login with one of my Yahoo! ID’s which i created January 2008 Yahoo! said that ID is not taken yet duh! i quickly recreated it. If it said wrong account name or password that would mean my account hacked by a cracker kiddo.
Since i have tons of Yahoo! ID i had to check em all by signing in one by one * damn it is boring* . I deleted many of my id’s at that moment and now i have like 35 (not any rare) . I use Microsoft excel to keep order them so i never forget. I never keep that file in my computers but in two custom flash disks which i never take out with me. This is cause if my computer hacked i will not lose any about Yahoo! and i have another back up on the other disk, and yes i know i am paranoid 
If you have lots of Yahoo! ID’s like me and didn’t logged in for a long time i suggest you to check out em all cause you may lost your favourite ID