End of last year I run into this issue along with another one related to LSA protection and code integrity check (which will be covered in another post).
This issue might be rarely, but you can run into even your environment is not large and even you followed the Preferred Architecture (PA) for Exchange and used the calculator. If you have this issue, it can have serious and unforeseen consequences and impact your setup.
If you want to read more about: I wrote about this on a guest post on the ENow blog.
The clueless guy 