What are the negative effects (if any) for leaving a prosumer comcorder powered 24hrs a day?
There could be some consequences to using the Canon XA10 24/7, although I don't think they are very likely to happen.

I can think of two things that might go wrong:


Even tough the LCD is off, the CMOS sensor inside is still working. This can generate significant heat and cause an overheat. However, most cameras have a built in protection that shuts them down in case of overheating, so it's not a real risk.
Depending on what you will be shooting it is possible that the sun will shine directly through the lens on the sensor for a long time. There's some debate on this on the Photo.SE site, but some think this can damage your sensor.