Many poeple have attempted to get ebays stance on this, the thing is that the auctions go up, and if you look at the user ids, not all have been sdc_ .
In some cases, where the usernames were not "sdc_" they showed up as random names but then "sdc_ " in the "my ebay" areas (but not all did).
Also, if they were some kind of cockup in the systems, why would ebay just delete the forum postings (over 10 removed threads so far) rather then just saying what it was.
Not to mention, even if you are running the same backend, for mutliple style sites, who would be stupid enough to allow the database systems from one, to be able to interact with another?
I run multiple sites myself, all using the same backend, and at no point can one "read" the others database.
At least not without someone doing a bofh on the system.