BusyBox settles another lawsuit

Yes, it's ultimately your responsibility, but you can still rely on a third party to deliver
on your behalf. We do it every day with courier companies, ISPs, and myriad other
organisations. There's a risk that they will fail you, and disappoint the customer, and in
that case you have to fix it (even if you also sue the third party for screwing up). But
there's often a benefit to letting a specialist do it for you which makes the risk worthwhile.

A site which says "The 4GB of GPL'd source code for our various products is now supplied by
Compliance.example.com, please go there" is OK (assuming you've actually made such an
arrangement with the site linked), whereas, "Most of our products use GPL'd code, you can
usually find the source code with Google" is not OK.