A lot depends on the biking culture of your area. Here the paths are used so often that announcing your pass seems unnecessary in most cases. I stay far enough to the right to communicate that anyone may pass me safely. Most don't announce their pass, which is fine by me. When I prepare to pass a cyclist, if I notice they're deliberately riding well to the right, I don't announce. Same with peds/runners. These are people who assume they'll be passed numerous times on the path, and I give them wide berth when passing, so it could hardly constitute buzzing.

If a cyclist/ped/runner is hogging the centerline, then I'll announce "passing" and allow them to make a decision as to which way to veer. Most will correctly veer to the right.

Oh, and when I prepare to pass I always check over my shoulder to make sure I can move over. I've approached packs of cyclists where I can't tell who's intending to pass. In those cases I always announce, and I expect anyone ahead of me to signal their intentions (by glancing over their shoulder before they veer to pass). There's nothing scarier than being in the middle of a pack of cyclists who don't know which way they're going.