Pentax issued this statement about the stains on the Pentax K-5 sensor:
"To PENTAX K-5 Digital SLR Camera Users
We would like to express our heartfelt appreciation for your patronage of PENTAX products.We deeply regret that the first shipment of our PENTAX K-5 digital SLR camera included some products with a stained image sensor — a problem which we believe was caused during manufacturing - causing them to occasionally produce images with spots which look something like water drops, and which users cannot remove with ordinary cleaning methods.
All users of these defective products will receive free repair at our service center.
We sincerely apologize for any trouble and inconvenience this problem may have caused. We also promise to do all we can to achieve the highest level of quality control in the future, and eliminate any worries our customers might have about our products. We sincerely appreciate your kind understanding and cooperation regarding this issue."