The AOL-backed chain of hyper-local news sites, including several that are operating or planned in the Bay Area, is on a hiring spree, according to the Newark (N.J.) Star Ledger, where Patch just opened its 100th site in Morristown, N.J.

Upstart hyperlocal ventures are increasingly vying for a piece of what they say is an untapped gold mine in local advertising dollars. Yet to be seen, though, is evidence that the sites can develop long-term, sustainable business models.

“Something like Patch was eventually going to happen,” said Kip Cassino, vice president of research at Borrell Associates, a media analyst firm. “Newspapers felt that as long as they owned the content, they were unassailable. History has proven them wrong.”

Patch was founded and bankrolled in 2008 by Tim Armstrong, a former Google vice president who became AOL’s chief executive last year. Under Armstrong, AOL quickly bought Patch for an undisclosed sum and pursued an aggressive franchising strategy, investing $50 million this year to expand Patch nationally.

And this from Forbes, which also has a story today about Patch:

“This is the largest area on the Internet that hasn’t been won,” said Jon Brod, executive vice president of AOL Local, Mapping and Ventures. “Amazon has commerce, and eBay has auctions, but a big part of your income is spent at home, it’s where you spend most of your time.”