When someone chooses not to post a real photo of himself with his writing it isn't necessarily a matter of "hiding". I don't choose to post a photo of myself, and I would venture to say that my writing (whether or HubPages or anywhere else online where I have material) - if nothing else - could not be more honest, open, and authentic. Although I have only rarely been questioned about anything I've written, I am prepared to back up what I write (with further clarification, references, etc.), knowing that anyone can either ask me to through Hub comments or else e.mail me.
Based on some of the "real" photos I see on HubPages and elsewhere, I (like many others) have reason to suspect that not everyone in those "real" photos are the writer. I have a perfectly acceptable face (one nose, two eyes - all the usual stuff :) ), so it has never even occurred to me that not posting a picture would be seen as "hiding". I suspect a lot of people are like me, though, in that many people are not very comfortable posting their face (and in some cases, their own name) out there for "all the world to see". Many people have a certain amount of "reserve" that has nothing to do with hiding.
As a writer, I want my words to speak for themselves. As a reader, I've occasionally had my curiosity about what another writer looks like; but, in general, I don't think I need to know that to know whether I like the person's writing.
My name makes it pretty clear that I'm a woman; and in much of my less "formal" writing I mention things like having children. In more formal writing I don't include information about myself; and when it comes to that kind of writing, again, I want the words to speak for themselves. I don't want people clicking past my work because they may think women write nothing worth reading or because they hate Americans - or for any other reason a picture may result in prejudice against my work.
I could point anyone to a few pieces of my writing where comments make it so clear that my woman's name, alone, does occasionally bring comments that the same writing, under a man's name, would not "inspire".
For writers like me, who want their words to speak for themselves (and for them, as writers and people, as well), not posting a picture should not be viewed as "hiding".