In an official statement, Ebay is asking users to reset there passwords because of a cyberattack that breached it's database. At least 145 million records have been accessed, making it the second largest cyberattack in history. The stolen records included passwords, email addresses, birth dates, mailing addresses and other personal information. However, financial data like credit card numbers were not included. The impact on eBay customers is not known yet.
If you use the same password for multiple sites, it is advised that you also change those passwords.