If a webshop using a deterministic wallet makes its master public key public (as it should),
By making your MPK public you've basically revealed to the world your entire sales data.
Only a fraction of the sales data are revealed.
If bitcoin transactions represent only a fraction of the sales (like cash transaction represent only a fraction of proximity payments), the world can only see the tip of the iceberg. And maybe the world will give credit to the merchant for its transparency and increased security.
Bitcoin payments could one day represent a larger proportion of sales of digital goods.
However, with digital goods, it could be a plus if content owners can audit the sales or the donations.