Cosplay Does Not Equal Consent.
My second year of Anime North I did a recognizable version of Roxas from Kingdom Hearts II (pictured left). The costume was very popular - it also helped I had a group with me doing Organization XIII. I had a few people ask for photos with just me, and I was ok with them standing back-to-back (very safe), and even an arm around my shoulder (which I am a-ok with). But I did have a couple of fans who were not within my comfort zone. Which pushed me to make the decision of not returning Roxas to Anime North. This character hasn't seen Anime North since then.
My problem was not with fanboys... but fangirls. I had a few thinking I was an actual guy, despite that you could see my binding. They eventually would get that I wasn't interested, or that I was a girl. But I had one who wouldn't leave me alone, trying to grab where was not appropriate, even putting her hand on my chest. Despite my protests telling her that I was actually a girl, she wouldn't take a hint. Luckily my boyfriend was nearby (who is quite obviously a guy!) and I grabbed him and kissed him in front of her. She left me alone after.
The other issue, which is what truly scared off me bringing Roxas back to Anime North - he might make a return one day - was the one who tackled me. I was literally tackled to the ground in this character. I heard the name "Roxas!" screamed and before I could really brace myself, I found myself on the ground, on top of my keyblade. While I approve of loving a person's character, tackling them to the ground is NOT ok!
And because I had people with me at all times, I encountered no problems. Since then I have been pushing myself with comfort. 2011 I did Lady Sephiroth, and 2012 was Kuja and Princess Velvet. This year, Ultimecia, and a new Kuja. And possibly Zafina. But I am taking precautions.
I have had people ask me for doing photos with me in my characters that show a little more. There is one that I liked where the guy was very respective of my friend and I (we were female Sephiroth & General Beatrix). He asked us politely if he could have a photo taken with us, and while we posed with our swords, he crouched down in front of us giving the thumbs up. This is very ok, as it doesn't make anyone uncomfortable, the fan gets a picture, and you are safe.
I've learned over time that there is safety in numbers. And while that's not always possible, it's a good idea. In Kuja and Velvet, I've made sure to have a friend with me. And each time it's been the same guy friend. Fanboys and fangirls are both problems.
Always taking precautions as you need per costume is a good idea. Some don't require it if you're fully covered, or you fit the character perfectly, because then you are less likely to be bothered - at least as experience tells me.
I'm only speaking from my own experiences with this. Others may have differing opinions etc. If you wish to share, please do!
But please do share your thoughts, opinions, experiences.... I'm curious what you have to say.