I personally think Adoptamac.com is not spam at all and quite beneficical to the old mac community. I see no reason to remove it from your sig.
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iOwn: GrayBook 2GHZ (Main Laptop), iMac G5 1.6GHZ (Main Desktop), iBook 1GHZ, eMac700mhz, iMac350, iMac233, B&WG3400mhz, BWG3350MHZ, iBook466MhzGrayx2, iBook300Mhzblue, Performa6214CD, Mac512k, MacClassic2, MacIIcix2, PM8100/110, PowerBook150, Apple][e.