Even if not needed for every package of a PPA there are cases where the depending PPA is needed for runtime dependencies. Such a case would be if a package is build against a library from the other PPA and also needs this version to run. Not mentioning that a PPA user might need the other PPA to fulfill runtime dependencies doesn't sound right.
Even if not needed for every package of a PPA there are cases where the depending PPA is needed for runtime dependencies. Such a case would be if a package is build against a library from the other PPA and also needs this version to run. Not mentioning that a PPA user might need the other PPA to fulfill runtime dependencies doesn't sound right.