As you go about establishing yourself on Facebook, it may be tempting to add your customers or clients as friends, or accept friend requests from them. Here are some things to think about when deciding whether or not to accept or send a Facebook friend request from/to a client:

Facebook etiquette
  1. Their Privacy: As a friend, you will have access to the details of their profile and be able to see most, if not all of their status updates (unless they are smart and using friend lists to filter the visibility of their posts and info.) Ask yourself - do you need or want that level of knowledge? Would your client be comfortable with you commenting on, for example, a photo of his or her children?
  2. Your Privacy: On the flipside, if you accept (or send) a friend request from/to a client, they will likely have access to your personal information and status updates. Are you comfortable with them knowing about your political affiliations? Your family? That you checked into a local bar? Will you be able to either keep your posts client-friendly, or use friend lists to limit what content your clients see? Is it worth the risk? 
  3. Facebook's 5,000 Friend Limit: If you have a substantial group of friends and are adding customers as friends as well, you may find yourself fast approaching the 5,000 mark - Facebook's upper limit. At that point, you'd need to start culling the list, to accept closer friends or more important customers. 
  4. Profile vs. Page: If you're adding clients as friends for purely business purposes, you could be violating Facebook's Terms of Use, which state: "You will not use your personal timeline primarily for your own commercial gain, and will use a Facebook Page for such purposes."
  5. Reachability: When you're friends with a client, it will be easier for them to contact you at random hours, whether via Facebook Messenger/Chat, wall posts or comments. You can use friend lists to limit your reachability, but consider that they might realize that they can't post on your wall and ask why. If they send you a DM, Facebook will show them that you've read their frantic 2am message, and they may wonder why you haven't responded yet.
It's up to you to decide if your clients can be your friends on Facebook. A good rule of thumb might be that if you wouldn't be friends with someone if they weren't a client, you should not have them as a Facebook friend. Personally, I do have some clients as friends and I use friend lists to determine what information is visible to them to avoid any potential awkwardness. Remember that when you're establishing your social media presence, identifying your agenda can help keep things clear. 
 
P.S. Speaking of privacy, with the introduction of Graph Search, rumors are, once again, flying about Facebook making private info available to the public. When you see people posting "Please Repost This" Facebook security rants, please direct them to Snopes.