While eBay has found no evidence that customer accounts have been affected, they are requiring that all users change their passwords. Each account’s activity will be suspended until the password has been updated.
For more information about this breach, the actions eBay is taking, and eBay’s recommendations to users, please visit their FAQ on the situation: http://www.ebayinc.com/in_the_news/story/faq-ebay-password-change
As always, if you receive an email prompting you to update or verify account information, use your web browser to navigate directly to the site (in this case, www.ebay.com) to do so. This is to protect you against phishers attempting to take advantage of the situation.