Existing Starwood Amex cardmembers can earn up to 2000 bonus Starpoints by adding cards to their account. The fine print:

1,000 bonus Starpoints will be awarded to your Starwood Preferred Guest Account 8-12 weeks after the first purchase on an approved Additional Starwood Preferred Guest Credit Card submitted with this application. The Additional Cardmember must make their first purchase with the Starwood Preferred Guest Credit Card within one year of Card approval. Bonus offer applies to first 2 Additional Card added on this application only.

Link (Via FT)