yep ByHost is part of the reason macs are so good with moving the hdd to another physical machine and booting off it. Machine-specific settings (like energy saver) are stored there and are customized for each computer. Though the reason why an app needs to store something ByHost can often be a mystery.
Those files, like most mac preferences, are created as needed when missing, so it's almost always ok to remove them. If you know for certain you don't own the machine they apply to anymore, it's definitely safe to remove them. But they're usually small and really not worth your effort?
You can sort ByHost folder by date modified and the current machine's entries should be on top. Anything below that might be fair game.
Even if you delete something your current computer is using, it'll just remake it, and you may find a setting or two somewhere has changed from the value you customized it to, back to its default value as the ByHost file is recreated automatically.
BTW, that folder is normally hidden isn't it? That's Apple's way of saying "no touchie!"
