I've been playing for several years now but I've never heard about this before. Anyway, one of my friends who plays bass told me that you shouldn't turn the volume knob on your guitar up to 10 because it will slowly ruin your amp for some reason. I've never heard this before but he said several guitarists he knows told him but he didn't know whether or not its true. So basically, is having the volume knob on your guitar all the way up bad for your amp?
My Random Gear:

-Epiphone Dot
-Epiphone `57 Les Paul Jr. Reissue
-Epiphone AJ-200 Acoustic
-Fender Hot Rod Deluxe
-DS-1 Distortion
Lie, the signal from your guitar is so weak it has to be "amplified" which is the job of the amp anyways, so it's doing what it's supposed to
Ummm...No. Cranking your AMP can be bad in some ways, like if you have a tube amp, it will kill your tubes faster. Or possibly blow a speaker...But cranking your guitars output signal (what your pickups do) basically won't do anything except affect your sound.
B-52 ATX-100
Mesa Oversized recto 4x12
Jackson DKMG (w/ BareKnuckle Warpigs )
Ibanez Acoustic

Feel free to add me or PM me.
Just so you know, electricity is like water. . . so if you have a lamp, bend the cord while it's plugged in and turned on and it will cut of the flow of electricity and the light will go off. . . tell your friend that. . . I think somebody was yanking his chain and he fell for it. . . I don't know where someone would come up with that ruining your amp.
Quote by paranoid joker

Metal, should kick you in the nuts, after you catch it messing around with your girlfriend.
and then make a sandwhich in your house and walk out.