My wife and I started about a year ago:
(2) Chase Sapphire 50K
(2) Citi AA Visa 75K
(2) Citi AA AMEX 75K
(1) Citi AA Visa Bus 75K
(1) Citi AA Visa Bus 100K
(1) Chase BA 100K
(1) SPG Personal 30K (not yet received card)
(1) SPG Business 30K (not yet received card)
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Total CC bonuses alone: 735K
Also opened a Citibank checking and savings and got 40K miles.
Our goal is to do another SPG Personal and another SPG Business for an additional 60K in total.
And we also have a hefty sum sitting in with BankDirect for monthly miles from AA...
Lately we've been getting a little more aggressive with the CC signups, especially seeing how in Creditkarma it's not affecting the scores much, if at all!