Getting museum and galleries to share content openly is problematic for a lot people in the sector. It challenges the boundaries of their institution, their curatorial control and their sense of the authority of their data. It forces then to be open to the idea that knowledge comes from different places and to accept that people may want to use their cultural content online in many different ways that have value to them specifically.
There are some institutions that already understood this challenge and are are beginning to be proactive and actively push their content into social networking sites. An article about how the Brooklyn Museum in the US illustrates this point.
The Museum are letting stuff flow out into social networking sites like Twitter, Flickr and it is having an impact on the level of active user engagement through the posting of videos, pictures, comments etc. What is particularly good is that the museum has put back onto their own site the many pictures their visitors have taken of their institution and posted onto Flickr.
They are embracing the community and being very open about its interpretations of their stuff, they are also improving their own search engine optimisation (SEO) which is always a big challenge for any website.