Potential problems with rebasing branch foo onto master, if master was previously merged into foo?

I'm designing a workflow for a long-lived feature branch `foo`. This
branch will have `master` merged into about once day. About once a
week, we rebase `foo` back into `master`.

Are there any problems to be expected in this workflow?  I have a
hunch the rebase back into `master` might be subject to potential
problems that I can't foresee.

I should mention that over 70 developers will be collaborating on
`foo`, spread across multiple, widely diverging timezones; any state
that requires all of these developers to coordinate / synchronize will
be prohibitively expensive for us.

Thanks, D