Dotted lines are useful for the overall business but I feel often the guy at the lower end of the line does not get the required credit for the work he does. I have worked in such scenarios where after a while the smaller guy is taken for granted and his line manager is not given enough visibility at the end of year reviews.

The dotted line allows requester to use a resource without having to cater to the other aspects such as trainings and reviews etc which feels like a lack of accountability to me. Problem is , if you want to be an exceptional DBA you need to be able to manage this situation effectively i.e the onus is on you.