We signup for various cards. Some just for the signup bonuses, others we keep for the ongoing benefits.

Some keepers are the following:

Chase Priority Club
Chase Marriott
Chase Hyatt

Non keepers: United. Chase Sapphire Preferred have 1:1 transfer w/UA & with the travel 2X bonus, the reason is obvious.

The above cards are for the annual free hotel night. Since the above cards charges annual fees after the 1st year, the Marriott & Hyatt are slightly better than a wash. The Priority Club is a better keeper due to not limiting category like the Marriott & Hyatt. and top PLT status keeping the card.

The real keepers & where we spend the money ($!) are the Starwood AMEX & Sapphire Preferred. If the other cards were as good as those, we would put some permanent spend on those.

As for the question of bloggers, I believe the banks are getting info about what works & what doesn't. I believe they already know but I believe they wanted some confirmation of what they already know. I could be wrong, however.