I've never used their web-mail. I now have two reasons for regarding Yahoo as a no-go area.
I used to use their Free SMS Service to send text messages from my PC. Suddenly, I had to have a username and login keyword and to get both I had to give all my details including my mobile number. At that point I backed out and said "Cheerio". I saw no reason for them to know that and only concluded that I would soon receive masses of spam texts.
Vodafone's "Vizzavi" seems OK and in the message you send there is only the briefest of Nokia adverts. And they know my mobile number anyway!
Far more irritating, however, is the amount of spam e-mail I am getting from Yahoo subscribers with unidentifiable names to undisclosed repicients and the like. I'm about to put a Rule in my Outlook Express to exclude all Yahoo addresses.
I don't think I know anyone who uses Yahoo...