If your house has a good Jr. program (or even just a decent one), talk to the pro shop owner about donating it. Then a kid who might not be able to afford his own stuff new might be able to get a decent ball for the cost of drilling. Other than that, yeah, you could just leave it. On the subject of taking from the rack, I'd check with the owner of the establishment - even if I were doing the "leave a ball take a ball" thing. Just seems like the right thing to do.
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9~
Keep your balls on the lane and your mind in the gutter!