I just read an article in the
newspaper (the
newspaper!) about those
evil, mean, nasty hackers who
infiltrate your computer (this time through
Windows file sharing) and use it for various purposes (storing files,
distributed.net, etc.)
The article also implied this is happening more now with DSL and cable modem connections, becuase they're always on. Well, I've got news for you, bucko: If you don't leave your computer on all the time, the Internet connection isn't on all the time either. If you're a casual user who maybe uses their computer 1-2 hours a day, and isn't relying on it for any services, just turn the damn thing off, okay?
Some people think you should leave your computer on all the time, claiming things like component stress and the like. I say, feh. A computer burns about 100 watts if it's not in suspend mode (if it's in suspend mode, the components will stress powering back up, anyway.) That's 2400 watt-hours a day, or 2.4kwh. At 10 cents a Kwh, that's 25 cents a day, roughly, or about 7 or 8 dollars a month. Over the 3 year lifetime of your computer, you'll have spent over $200 trying to prevent the components from being stressed. You're basically taking the chance that any potential failure you'd get by turning it on and off is worth more than $200, and that leaving it on isn't itself a problem. I live in a house without air conditioning and if I left my machine on all the time in the summer it would definitely be damaging--much more so than the anecdotal "component stress". Buying an AC just to cool my computer when I'm not using it would be even more wasteful. And yes, I know conservation isn't in vogue unless you live in California right now, but do you really have the right to leave your computer on, causing utilities to have to build more polluting power plants in other people's backyards? You don't have to be a tree hugger to see the sensibilty of using less power so our electrical grid remains stable.
Now, I'm not saying you shouldn't leave your computer on all the time if you're actually using it, as a home server, or for serious work, but I really think leaving it on all the time to run SETI@Home is stupid. And if you're a user who doesn't understand network security and has DSL or cable modem Internet access, you aren't cool enough to leave your computer on all the time. Besides, DSL isn't really always on if you're using PPPoE to connect--it's just like a regular dialup connection. And you probably don't have a static address either.
I guess I'm just mad at the assumption that you should leave your computer on all the time. For most people, there's no need. Only do it if you have a tangible reason; otherwise, save the energy, go out, take a walk, whatever.