Yahoo! bit the big one for me long ago..
When Yahoo! held hostage accounts "synchronized" with AT&T, that was the last straw for me, way back in 2005. We had email through Yahoo! in some of our offices, where that was the only way we could provide services for remote offices. We didn't have them on our head office server yet, because they didn't have the necessary router, or broadband for such a connection. We were on a budget and unless the community population and/or services met a certain category, we didn't use our company email server.
After we switched from AT&T to a broadband service that had just been built in one of the far flung communities, we discovered all email was going to be lost because Yahoo/AT&T refused to release it as a web based email again. Yahoo! and AT&T were both sued over this and lost in court but it was too late for our hapless remote offices. We had to rebuild from scratch, and we never forgot about that. Never again will I or anyone I know, recommend Yahoo for web based email again, even though now - you can supposedly free it up after that court case. They really stuck it in the dirt with treating so many people that way. And then they wonder why their market share keeps going down.
There is nothing more irritating than having to delete Yahoo! as a search engine in everyone's browsers too!! It keeps coming back and taking over the browser like that 'Ask' tool bar that was finally declared a PUP a few years ago. You cannot engender good will acting like this, but Yahoo! never seems to get it. Just like A-Hole, er I mean AOL did years ago. The pestilence will finally be eradicated by their continued bad behavior, and everyone jumping ship like a bunch of drowning rats! Thankfully we finally instituted Outlook Web Access 2003 email for remote dial up offices, so we could get an SSL connection and still use our central server to control our remote offices. Never again will we ever trust an outsider like that for email service - besides I would bet that the HIPAA regulations have by now blocked using such insecure services now anyway.