Yesterday Yahoo! announced that it will be offering 100MB of free mail storage to its free user base. Currently Yahoo! is offering 4MB, but recently Google came out with Gmail, a free Web based email service with 1GB (1000MB) of storage. In an attempt for Yahoo! to keep their users, Yahoo! announced that they will be bumping up the free storage from 4MB to 100MB.
I personally believe that this courtesy on Yahoo!'s behalf will make a huge difference with keeping their user base. In addition, Yahoo! will be offering "virtually unlimited storage" for its paid e-mail customers. "Virtually unlimited storage" is going to be limited in some sense, but as the CNET article points out, Yahoo! is trying to "make storage quotas irrelevant to users."
I think the 4MB to 100MB upgrade will make an impact on the Yahoo! mail users. Google still has this whole privacy debate going on and they are still only on invite only terms. Yahoo! is established and the 4MB user is really going to love the extra 96MB. Personally, I do not know how anyone can live on 4MB, but that is for an other story.