The term "ghosting" may be relatively new, but the concept -- someone suddenly and inexplicably disappearing from your life -- is not. In the past, a total halt to communication with a friend might leave you feeling concerned that something bad happened to him/her. But in a time where our devices have made us more accessible than ever, it can leave the person who's been ghosted feeling rejected or unworthy. The Sugars discuss ghosting with the essayist and cartoonist Tim Kreider. He's the author of "We Learn Nothing," …