The first example is one that has actually seemed to turn into a phenomena of it'd own, couch surfing. I only learned of it last quarter when one of my partners for a project explained to me how he was hosting a couch surfer that was coming to visit Savannah. The idea itself is interesting, members have the option of supplying information and pictures of themselves and of the sleeping accommodation they may offer, if any. More information provided by a member, and other members, improves the chances that someone will find the member trustworthy enough to be his host or "surfer." Members looking for accommodation can search for hosts using a few different qualities such as age, location, gender and activity level. The surfer is able to stay at the host's house without having to paying any money, except maybe for replacing the food they eat.
CouchSurfing provides travel guides and forums where the members are able to seek travel partners or advice. CouchSurfing's main focus is in "social networking" and members organizing activities like camping trips, meetings, and sporting events.
The website is already very successful and already has 3,072,679 members participating on the website. On the other hand I can't get past the fact of people lying about who they are and the possibilities of you not really knowing the person who's house you are going over. My partner had said he had had some sketchy people who he hosted for and there has even been raped when going into a strangers home. Not to mention that your home is supposed to be a safe place for yourself and your possessions, I may be paranoid but I would never want to leave someone I didn't know inside of my house where they're able to do as they wish.
I also found another website called TravBuddy that specializes in connecting travelers. The site allows users to find travel buddies planning to travel to the same places at the same times, to create travel based blogs, upload photos of their travels, and review bars, restaurants, hotels and various attractions on their traveled areas. The site has nearly 1,350,000 registered contributors and provided free access to over 65,000 blogs, 17,000 travel reviews, and 750,000 travel photos. I feel like this site is successful because it appeals to a very specific group of people who are passionate about traveling and will want to get opinions or reviews of places they will be going to. I don't see anything that can be a downfall of this website, except for the immediate well known dangers of any social networking site, and I feel like this site will only get more popular with time with it's usefulness and the word of mouth of the users.
In learning more about social media I found this article called "50 ways marketers can use social media to improve their marketing." Reading the list, there were some interesting suggestions that were made in how to optimize social media and how and when are the right times to use it.