One of the super interesting choices Swipely made is that they don't give users a choice to pull in non-credit card feeds. If you want to play, you've got to go all the way. Blippy on the other hand, at least as far as I can tell, wanted to let users warm up to Blippy by adding more innocuous feeds like their iTunes purchases or Netflix queue.
I actually think Swipely tact is super smart. In a way, the other feeds Blippy lets you pull in act as a privacy signal. Because I can add feeds that don't feel that private or sensitive (like my iTunes purchases), it creates a baseline for my privacy comfort. I then compare sharing my credit card feed against my iTunes feed, and it feels like a huge difference.
But with Swipely, you don't have the same frame of reference. Are you in, or are you out? My guess is they'll have a lot more success getting people to enter their credit card numbers, not because of their alleged super-duper security, not because they let people check each item before it gets pushed to their feed, but because when compared to nothing, adding your credit card number doesn't feel too crazy.