Well from the eyes of a Facerbook page administrator it's not always as easy as it seems.
I've been a fan of opened walls for a long time. I think it's nice to see when a brand invites people to post, not only comment on what the brand dictates should be on the wall.
I also assumed that the engagement rates of the brands with the opened walls would be much higher than the brands with closed walls...Until I did a bit of research.
I researched 30 brands and wrote down the Number of fans, the number of People Talking About the brand, calculated the Engagement rate and made a note on each brand whether their Facebook page wall is opened or closed to the public. I then highlighted the brands with an engagement rate higher than 10% in green.
Out of the 30 brands I researched the one with the highest engagement rate is Toyota. Second up is McDonalds and Third place goes to Nestle. All of them have their walls opened to the public.
However, what might come as a surprise is the low engagement rate on brands with opened walls such as Oreo and Skittles. And the relatively high rate of brands with closed walls, such as Nike, Adidas, Gucci, Luis Vuitton and Playstation.
Also note that two brands from the same industry, Playstation and Xbox have almost the same engagement rate even though one lets it's users post and the other doesn't.
Obviously there are more factors to take in consideration to extract some conclusion for this.
What content strategy is in place? Does the brand respond to people? How often do they post?
At the end of the day there are various things to take in consideration when deciding on the wall settings.
If you're a brand with millions of fans it's likely a hot space for spammers, advertisers and freeriders who all want to be in the spotlight if only just for a moment.
Does your brand have the resources to monitor the wall constantly and take actions when unwanted material is posted? If so, it could push up the engagement rate a bit to have your wall opened.
If you don't have those resources and you still choose to keep your wall opened, you MAY end up with something that looks more like a scribble wall instead of a professional Fan page.