The only real problem you can run into is if someone is boneheaded
enough to misconfigure their routing to do per prefix load splitting
across WAN links or worse yet across providers. Again, such people
don't deserve to stay in business (since *all* TCP traffic from their
network will suck), but they do exist. The common newbie mistake is
to configure per prefix load split among two default routes. Westnet
used to do this many years ago. Some small network in Florida did
this more recently.
Minor correction but big difference in meaning. Per prefix is fine.
It is per packet load split that causes trouble.,