10000 Bonus Points! American Express preferred Rewards Green Card

Got a postcard from a friend with a 10k bonus points offer for American Express preferred Rewards Green Card.

http://www.americanexpress.com/greenfriend
unique id: 3072314205
Offer expires 10/14/2007

Bonus will be awarded 6-8 weeks after first purchase.

There's an annual fee of $95 (including their famous free first year)
My question will be...How soon can I cancel the card after I get the points, due to this is a card with no credit limit which may look bad on CRs if used.

Can we all use the same unique ID? It does say you were referred to this offer by a friend or family member

fmbaig21 said: Can we all use the same unique ID? It does say you were referred to this offer by a friend or family member

He got a couple postcard, the codes are all the same...I think it should be green.