Well, a picture looks like a person from /one angle/, in one particular lighting.  People we already know in 3-D, we tend to think their pictures look like them b/c we know how their many angles look.  Looking at someone first in 2-D, you can be surprised by the way they look in 3-D b/c there are so many angles you're /not/ seeing.

Also, there is the issue of the fact that depending on how close the camera lens is, it tends to magnify whicever features are closest to the lens.  That can switch things up too.

they pick the most flattering angle?

My experience has been, for the most part, just the opposite.  I don't think most people, probably myself included, choose their profile photos wisely.  

i've been on internet dates and been told "wow you photograph well". harsh, but yeah i do tend to use more flattering angles for profile pictures i suppose. The point is, that angle of me EXISTS, its there. And if they're not the type to see the good side, well they're not going to be very fun to be around, in my experience.

I would completely agree with feeling put out if the photo was old or before the weight gain / hair loss. Not because i'm not comfortable with a squishier man with excess forehead, but just because it's dishonest.

As an overgeneralisation, women tend to present themselves as more attractive than they really are, and men tend to present themselves as more single than they really are.

For women, part of it is the reality that many men do not read. They won't read any part of your profile at all. They check out the picture, and if they like it they'll write. So if your real charm is in the way you think or the things you like and might have in common with someone, a guy will never get the chance to find out unless you have a cute picture on your profile. Because the picture is the only piece of information he will bother paying any attention to.  Which puts women trying to date men who don't read in an awkward position.  Because given the choice of responding to Kirstin Dunst or an otter's anus, the illiterate guys are always going to respond to Kirstin Dunst.

So. Where this gets taken to the extreme of posting pictures of someone else. Sometimes it's just not thinking ahead. The otter's anus posts a picture of Kirstin Dunst and doesn't look far enough ahead to what happens when she gets a date.

And sometimes it's something a little more subtle. Maybe all she really wants is attention, and Kirstin Dunst will get that for her. Then she ends up with a real-world date, and that wasn't in the plans. Oops. Or maybe the otter's anus is so used to being rejected that she has to trick herself into using internet dating. She tells herself that she's really just going online for attention, that she doesn't actually plan to meet anyone. Secretly she would like to have a boyfriend of course, but that would be too painful to admit. So when someone looking to shag Kirstin Dunst makes a date with her she can't turn it down, but then she has a problem - but without the experience or self-confidence to deal with it effectively.

Regarding wanting attention vs wanting dates: yes, it's sometimes true. As a man you might not spend much time reading men's ads, but a whole bunch of them say "not into games." Which is what happens when men who want to empty their balls respond to profiles posted by women who want to be flirted with. They become confused, annoyed and bitter.  

Anyway. Does this help?

(Posted by someone who did the internet dating thing, painfully, for years and eventually found The One - yes, online, and using all her own pictures.)

It is amazing how people seem sooo different in their photo's (I've often gone back to profiles just to see where I got confused).  That being said, it really is hard to convey in a snapshot all the nuances of a persons self expression so I try to be a little forgiving.

Personally - I don't care so much for the perfect photo as for a good range of photo's illustrating who they are at various moments and that they are attractive [in many ways / as attractive is unique to all].  That is worth so much.