The transaction info available on the Starbucks site and mobile app is pretty limited, but I can see that the transactions are listed as "In Store Purchase". For example:

http://cl.ly/3H1j3g443X0y0O3j2M2L

Unfortunately, there is no info about which stores the purchases were made in, and the history only goes back about 20 transactions. It does look like some people are making large purchases, which is jerky, but not totally unexpected.

Thanks, j