Users of the do-it-yourself trading site collective2.com received an “urgent” e-mail at a few minutes past noon Wednesday notifying them that the company’s computer database had been breached by a hacker and that all users should log in to change their passwords immediately. That e-mail, from Collective2 LLC founder Matthew Klein, stated that the information accessed by the hacker included names, e-mail addresses, passwords and credit card information. In addition, the e-mail went on to state: “We have contacted federal and state law enforcement authorities, who we hope will track down and prosecute the person responsible