Most social media websites give you an individual profile page alongside the option of befriending other site users. The adding of someone as a ‘friend’ on a social media website is not just an empty gesture. Usually when you add someone as a friend, you’re giving them greater access to you through the social media channel.

For example, some Digg users set their message inbox as ‘friends only’, so you can only ’shout’ or communicate with other users through the site when they have added you as a friend. Only when someone on Twitter ‘follows’ or adds you, will you have the ability to send them private messages or view his/her updates, if they are protected.

In sites like Facebook, adding someone as a friend allows them to see more of your profile (depending on your settings). Befriending users on Youtube allows you to follow their rating and favoriting on videos, while also allowing you to more easily share content with one another.

In general, when someone adds you as a friend on a social media service, you gain some or all of the following benefits:

Access to more data. You get to view more data on the user, some of which may be intentionally obscured from the public or other non-friend users. This allows you to network with the specific user in a more intimate and personal setting.
Greater communication options. Depending on the social site, when someone adds you as a friend, they open up more avenues of communication. This adds a greater level of interactivity: you can connect with the person who added you through private/direct messages, instead of the highly visible public channel.
Recommended content. When someone adds you as a friend (and vice versa), your activity or actions on the site may be recommended or ‘pushed’ towards the other person in some part of their admin panel or profile. This means that you’ll get greater visibility automatically whenever you use the social website.
Greater Social Proof. An auxiliary advantage of having many fans on social media websites is social proof, especially when the social site itself ranks the users according to the no. of followers/subscribers they have. Popular and visible users tend to accumulate friends more easily than unknown users.
Basically, you have nothing to lose and everything to gain when someone adds you as a friend on any social media website. They are giving you permission to share messages with them while bestowing attention on your recommendations/actions within the social site.

If you’re trying to get maximum visibility for your message, develop a popular social profile that has a large amount of fans in order to take advantage of the innate advantage that comes from communicating with a large number of people at once through a specific action.

You can see this most easily in highly subscribed Youtube channels. A video can easily rack up over 10,000 views in one day if it is released by a highly subscribed channel owner. Similarly, marketers or web personalities enjoy increasing their Twitter fanbase because they benefit from the influence they derive from consistently wielding a large amount of attention.