By Bill Rigby SEATTLE (Reuters) – In the last week of August, Twitter entertained dozens of potential young recruits at a chic studio, while Facebook served drinks and snacks to job-seekers at its own office. More than 175 showed up to a similar event at Google in June. No, Seattle, home of Microsoft Corp and Amazon and fast becoming a second home for Silicon Valley companies looking to access the citys plentiful pool of relatively cheap tech talent. Microsoft alumni are now running the Seattle offices of Facebook Inc, Twitter Inc and Google Inc, and they look to their former employer as a source for new talent.