OAKLAND -- Democratic presidential candidate Barack Obama publicly urged his supporters today not to contribute to independent and unregulated groups - particularly so-called 527 organizations -- that are currently raising money to aid his cause, saying that if backers give directly to his campaign instead, "we'll all be better off.'' The Illinois senator's comments came in response to a Chronicle story published today that detailed an effort by wealthy Bay Area backers to create a 527 group, independent of the campaign, to raise large donations and expand voter registration and turnout for Obama in the February 2008 California presidential primary....