Three mid-level bankers in Goldman Sachs Group Inc’s technology investment banking group in San Francisco have left to take positions at ride service company Uber Technologies Inc in recent months, people familiar with the matter told Reuters. The bankers are the latest to leave Wall Street banks for Silicon Valley startups, where the lure of more flexible hours – and in some cases stock options and share grants – can be hard to resist. Uber, currently valued at around $51 billion, said in August that it expected an IPO within 18 to 24 months.