For freelance models, social networking sites are great for self-promotion.
Some sites are more appropriate for promoting yourself as a model than others. (Please note that this post is based on my own personal experience with social networks).
A few things to remember before joining a social network as a model:
~Your modeling goals.
~Who you would like to meet.
~Why you want to model.
~Be realistic in your expectations.
The biggest issue with joining social networks as a model is that sometimes you will get offers from people that you don't want to work with, which will end up wasting your time.
Another thing is that anyone can be anything on the Internet, and it is very important to test the legitimacy of every job offer that you get by doing a Google search of the person who sent you the email. You should also Google that email address to see what comes up. Legitimate people usually have email addresses in the format of email@example.com and not firstname.lastname@example.org (or gmail or hotmail).
Also, remember that legitimate fashion agencies do not send modeling offers via Facebook, Model Mayhem, Myspace, or other networking sites. You have to submit yourself to such agencies, and they have hundreds or even thousands of people like you submitting every day.
Two of the most popular social networks for models/photographers/clothing designers/make-up artists are ModelMayhem.com and OneModelPlace.com. Additionally, there is also Ujena Talent (although there are not a lot of Canadian models/photographers on there).
There are also many websites which attempted to take the design of Model Mayhem and reproduce it. However, Model Mayhem is one of the first, and it has about 2 million members, so if anything, that is the one to focus your efforts on.
The idea of social networks is that you have to be...well, "social". Which means that you should comment on people's portfolios, pictures, use the forums (but don't troll or create drama), express interest in working with people, and add them as friend.
If you join a networking site expecting that people will flock to you like crows to a piece of bread without any effort on your part, you are highly mistaken. These sites have a lot of members, and you have to stand out (in a good way) and be active to be noticed.
Myspace is, at this point in time, pretty useless for promoting yourself as a model. It worked for Christine Dolce when it first began, but that time is done. Now, Myspace is flooded with bands who spam your comments/messages and girls doing the duckface with self-shot pictures saying "Look at me! Add me!". I have a Myspace account, but I can tell you that I have not booked any work through it. However, it has brought a little bit of traffic to my blog, so that's why I haven't deleted it yet.
DeviantArt is good for checking out other people's work for inspiration and having a large watcher list means that your work gets seen by many people each time you upload something new. Although you may not book high paying shoots off it, it is OK for growing your web presence.
Facebook now allows almost anyone to create a "Business Page" where other Facebook users can "Like" it. (It used to be called a "Fan Page" but I don't like to call it that). When you have a business page on Facebook, you will get a lot of traffic to your website and/or blog (which increases your search engine ranking, making it easier for people to find you), which can result in more shoots. For example, I saw a huge spike in blog traffic as a result of having a Facebook page, which is just one more place for my photos to get seen.
With a Facebook page, one of the key things that keeps people coming back and clicking on your links/pictures is frequent updates. When I say "frequent updates", I don't mean that you have to post every detail of your day on there (it's not Twitter). One or 2 updates a day is good, or even one every 2 days. When you post an update, and a "fan" likes it, it will show up in all their friend's news feeds, which creates more exposure for your page.
Twitter is very interesting because you can send out short, frequent status updates, and if your updates are interesting and appeal to the masses, then you can certainly develop a large following. With a large following, there is a greater potential that your portfolio links will get seen and clicked. Don't just follow everyone on Twitter though. When you are looking for people to follow, make sure that you only follow people who have similar interests to you or who already follow some of the people that you are following. The reason for that is that they are more likely to follow you back.
Then, there are also niche-specific networking sites that can help you move in the direction of modeling that you would like to take. Some examples include sites that are dedicated to fitness models, bodybuilders, fetish models, bondage, and so on. I don't know much about niche networking sites, although I do have an account on Bodyspace.com, just so I can read all the fitness and dieting tips, and see what's new in the world of fitness.
In summary, with social networks, you get out what you put in. Just make sure that you are channelling your efforts into profiles that have the highest potential of being seen by whatever your "target market" is. I can't tell you what your target market is, because that varies between models (and businesses in general). Use good judgement, and communicate with people who shoot/do what you want to shoot/do, and most importantly, have fun with it.
Do you have anything to add? Want me to expand on something? Let me know by commenting on the article.