Sara FischerTechCrunch is one of the most influential tech news sites in Silicon Valley. Photo: Jaap Arriens/NurPhoto via Getty ImagesYahoo on Friday said it has struck a deal to sell TechCrunch, the 20-year-old tech journalism site, to Regent, a media investment firm.Why it matters: Yahoo's business centers mostly on aggregation. Journalism isn't its core focus. Zoom in: Regent is trying to pull together a portfolio of tech news sites and is eager to invest in news. Earlier this week, it acquir...