Twitter has seen a surge in the number of active users, Twitter exec Dick Costolo said on Thursday.

Social Security debate reignited with Rick Perry's critique of Social Security as a Ponzi scheme.

Payroll taxes would be slashed for workers and employers, under the Obama proposal. Besides payroll taxes, the plan calls for $105 billion in public works and $50 billion in renewed unemployment benefits.

AP - Attacking a deepening jobs crisis, President Barack Obama challenged a reluctant Congress Thursday night to urgently pass a larger-than-expected $450 billion plan to "jolt an economy that has stalled." He urged lawmakers to slash Social Security taxes for tens of millions of Americans and for almost every business to encourage hiring.

AP - President Barack Obama's promise Thursday that everything in his jobs plan will be paid for rests on highly iffy propositions.

AP - U.S. officials said Thursday they were investigating a credible but unconfirmed threat that al-Qaida was planning to use a car bomb to target bridges or tunnels in New York City or Washington to coincide with the 10th anniversary of the Sept. 11 attacks, the first tip of an "active plot" around that date.