Should a photo be required before sending a contact request?

Only if you want people to accept you as a contact.

It helps me to see the person I'm talking with before I start talking or accept the request. RP isn't so bad for that, but on FB I see people's profile picture look like a car. I've sent more than one message to potential contacts on FB like this. "So you're a transformer. That's cool. What do you really look like?"

I like a photo so I can look at it and your history for approximately two minutes, then make a decision on your career and your future. I kid, I kid.

SFC (Join to see) , I said yes, but some don't for reasons they only know, however some don't own cameras, some don't own there own computers and are using a public or a friends, some don't know how to put an image yet and some don't because they just don't want too, it's not that their hiding its just that they don't want too. :)
But picture or not if I get a request it is 100% Accepted by me all the time.

Absolutely

never really thought about it

I think so

It doesn't bother me much considering 95% of the people on here already have photos.