Switching off will damage the PC or data?
No it won't. Switching off and switching on puts no significant strain on the PSU or components.
It will cost, on average, £9 extra per year in electricity bills for having just one computer on standby.
it is estimated that the 1.7 million computers that are not switched off after use. Use 700,000 tons of Co2 emissions on standby. the equivalent to 120,000 Chelsea tractors or the exhaust emissions from a city the size of Liverpool.
Source. This months PC pro.