A couple of years ago I got the travel bug and couldn't find anyone to go with. I went to the Dominican alone, although I met my travel agent and hung out with him for a couple of days. I decided however that travelling alone wasn't as much fun as I thought it would be. I decided to go to NYC next and this time (alone again) signed up for a couple of massage courses. I do massage and reiki for a living and spent four days being massaged and expanding my repertoire of healing skills, as well as meeting some locals and doing some things that were not touristy. If I travel again alone I will do it again. It's a great way to see new places and learn new things too!
I also arranged on the NYC trip to meet a couple of men that I knew from the States through dating sites (I'd talked to both of them for years and previously met one of them in Toronto). I had dinner with both of them. As long as you do it with safety in mind (meeting in a public place etc) then it's a great way to travel without being alone!