I'll try to explain my own point (sorry if my language is not perfect, I still do some mistake in English ^^")
1 - I don't know exactly what is a booth-babe. Are they the ones in cons that, for exemple, wear cat ears and give you some flyers about a product ? Or are we talking about cocacola babes who give you some bottles when you visit a con ?
In fact, I think the 2 possibilities are parts of the costuming cons like Comic Con. I can just talk about Paris (France) Comic con but I guess it's the same as SDCC, just not the same size

. What I mean is that they are not wearing costumes to interest you directly making you wonder if they are fans, geek, etc. or not but they make you say "hey ! this company/stand/market/... was great ! look the picture I took of their booth wearing this character tshirt/costume". It is just publicity

and, at Paris Comic Con, they really play the game of being a part of our community even if they do not do costuming the rest of the year.
One day, at a private party, my 501st garrison were asked to participate. So a friend and I took our armors and went to it. A girl was here to play Ben 10 in a costume like Mickey (you know, with a big big head and all the body covered). She was here only for money as she was a "booth-babe". She told us that she does it only for her company but we had a great time talking with her and partying with here for the guests. She was interested by "our world" even if she only wanted to do her job knowing nothing about Ben10
Booth-babe or not, she was costumed so she was a cosplayer during 4 hours like us, that's it
2 - being geek to "earn" the right of wearing costume ?
Ho god ! :facepalm How can someone say that ? Everybody (almost) was young and wore costume for parties and carnival at an age you cannot be considered as a geek. We just continue this dream when we grow up. That's all

And for those who think you have to know the story of your character, no you don't. If you just wear the costume because it is cool, no problem

After that, if you want to make a conquest or something that evaluate your hability of playing the character, then you have to know a little of him/her. But in general, the costume says all you need to know. For exemple : a girl with a gun will not play a princess, that is logical
The better example I have so far is my girl friend who knew nothing about star wars (exept that Vader was a bad guy with a big voice) but as she came with me sometimes to star wars events, she told me that she wanted to make some costumes (from anime, movies and SW). No, she learnt a lot about SW just by coming with me and so, asking about some characters she like the design. And on the top of that, she is making a Darth Talon costume even if we don't want to buy the comics. We only know that Talon is a sexy sith so she will play it as well. She only asked me about the twileks and their way of life to take some poses when pple will take pictures. That's all.
The important thing is to have fun with others and talking about the hobby
3 - About costume "quality" : My bad ...
A friend of mine who begins in our hobby told me that I'm a little harsh with some cosplayers when I said something like : "this captain america doesn't have the attitude a Cap.A must have" or "look, his/her costume is really cool but, there are some points here and here, and here..."
I think I forgot the fact that everybody do it as it can, and it must be fun to do it. And I have to apologize for it. The first costume I did was not so good at all so I have to remember that we all do our best and if we like this hobby, our skills will grow up. So as I said before, just have fun with the others and don't care if they are geek or not, or if they are here to sell or promote a company during a con.
"This is where the fun begins !

"
PS : sorry again for my possible mistakes ^^" I hope my point is understandable
