From the announcement:
The lives and activities of communities are increasingly documented online; local news, events, disasters, celebrations — the experiences of citizens are now largely shared via social media and web platforms. As these primary sources about community life move to the web, the need to archive these materials becomes an increasingly important activity of the stewards of community memory. And in many communities across the nation, public libraries, as one of their many responsibilities to their patrons, serve the vital role of stewards of local history. Yet public libraries have historically been a small fraction of the growing national and international web archiving community.
Read the full announcement here.