Our company runs a business similar to Yelp but limited to a regional area. Currently we are thinking of licencing our Point of Interest database under a free licence. 

Of course that would mean that our competitors can take all our POI data and put it in their database. But we do not see this as a big problem, because they can do it (illegaly) also by crawling our website.

What are our expectations? Mainly a higher motivation for the user to contribute information and a improved image.

Do you see any other advantages or disadvantages?

edit: Thank you very much for your answers. Unfortunatly it was decided not to open the data.