SAN FRANCISCO (Reuters) - Groupon Inc shares jumped to their highest level of 2012 Thursday as the daily deal company got a boost from social networking euphoria sparked by Facebook's IPO filing. Facebook filed to raise about $5 billion Wednesday in what would be the largest Internet IPO ever. A possible valuation of $75 billion to $100 billion for the world's largest social networking company encouraged some investors to lift valuation estimates on other companies in the sector, according to Sameet Sinha, an analyst at B. Riley & Co. ...