True.
I wouldn't want to speak for Beth, but as a photographer, I know that screen capture will be a significantly lower resolution than the original photo. Dowwnloading a jpeg (or TIFF or RAW) will generally allow for a higher resolution photo that can be resized and printed. Typical display resolution is on the order of 72 dpi, while printed photos are usually >300 dpi.
So, as a photographer, I personally am less concerned about screen capture than downloads. I shoot in raw (and scan to TIFF), but what I put on the web I downgrade to a "reasonable" jpeg & watermark with a photo program. Won't stop someone that's determined, but they also won't get the best quality photo.
I have one different view (and tolerance) for folks seeing and using my photos. Some I don't release at all (at least not yet) - that's especially true for ones going into my "project". My view is that since the dawn of photography it's been possible to "copy" someone's work - with high quality cameras, one can take a photo of your photo. Digital makes it far easier to copy. Very hard to stop, even with DRM. So my theory is that I don't mind posting lower resolution, watermarked pictures because the folks that are interested in buying will want the high quality, clean ones.
I think I understand Beth's concern, and I fully support what she seems to want to achieve. If you plan to sell your photos, you don't want someone to download and get for free.
Given FB's premise of existance, I don't ever see them doing anything that would stand in the way of "sharing" of content. Heck, within the last 2 weeks, they eliminated the policy that allowed some companies to prevent comments to their walls.