Regardless of what you may hear, its perfectly safe to have WC24 enabled if you have homebrew installed. Nintendo is not in the habit of snooping sleeping Wii's during the evening.
The main resoning behind turning WC24 off is that while it is on, the wii is only in stand-by mode, so its still powered and produces heat while it is visually "Off". I argue that Nintendo was aware of this when they made the Wii and wasn't concerned about the heat output. I for one still have my WC24 on, and experience no problems. But to each their own... If you dont want or use its features, why bother?