The offer:

Bank of America currently has a promotion for its Worldpoints cards providing $50 cash-back (via a $50 credit to your credit card) 8-12 weeks after your first purchase.

The fine print:

§§§ To qualify for this offer, your new account must be used to make any purchase or cash advance transactions (including balance transfers; which may include transaction fees within 45 days of the account open date). Limit one (1) item per new account. The Bank of America WorldPoints™ Platinum Plus™ MasterCard® Credit Card offer is subject to application approval by FIA Card Services, N.A.. Upon qualifying, a $50 credit will appear on your Bank of America WorldPoints™ Platinum Plus™ MasterCard® Credit Card statement. Allow 8-12 weeks from qualifying to receive the promotional credit.

The link:

http://www.bankofamerica.com/creditcards/