Remember Blippy, the social shopping service that works by sharing your credit card purchases with your friends and the wider Web community? It couldn’t work. Right? Well, in the past week a direct competitor, Swipely, came online in full force testing-mode to challenge Blippy.

Both companies aim to publish shoppers’ credit card purchases on their network of friends and associates. Shoppers can check out where their friends are shopping, when, and what they are buying then start a conversation about it. Angus Davis, CEO of Swipely, says that the point of the postings is to “add value to every swipe” by making this publicized information more useful for you and your friends.

At this point, the differences between the two companies is meager at best, so how they will differentiate themselves is still somewhat unclear. The biggest difference seems to be Swipely’s keen determination to convince you that its service is more safe than Blippy. They are doing this in light of Blippy’s blip-up last month when it accidentally started releasing peoples’ credit card numbers along with their transactions. Oops!

In fact, where Blippy automatically posts all your credit card transactions and the amount of money you spent, Swipely asks your permission to post each swipe and it doesn’t display the price you paid for your purchase.

But where Swipely is being careful to give people more of a choice what they publish, it looks like this may just be a tactic to show they are safer to get ahead of Blippy at the starting gate. Publishing “how much” has unmistakable advantages for shoppers and for companies. Shoppers can show off their deal-hunting prowess and companies can indirectly advertise their sales. Besides, a shopper may find that they want the amount published in the case of, say, donating to a charitable cause. In fact, Davis even hinted Swipely could publish “how much” in the close future.

If this tactic actually works is yet to be seen. Blippy is much more popular that Swipely on Twitter ( Blippy’s 3,380 followers to Swipely’s 436), and Blippy has much higher site traffic (as seen bellow):

But Swipely does have big backing, following a recent investment of $7.5 million in the start-up by First Round Capital, Greylock Partners, Index Ventures and several angel investors. The I’ll-show-you-mine-you-show-me-yours social shopping model could be around for a while.