I imagine Yahoo is feeling the heat of GMail going public:

Yahoo Inc. will increase the inbox capacity of its free Web mail service for the third time in the past 9 months, now raising storage to 1GB, exceeding Microsoft Corp.’s Hotmail and matching Google Inc.’s Gmail.

Yahoo Mail users all over the world will begin to see the larger inboxes between late April and early May, said Brad Garlinghouse, Yahoo’s vice president of communications products.

(Via MacWorld.)