I contacted the vendors lately and I can as well post this information here.
Virtuoso Cleaner and Virtuoso Polish both are silicone-free. While contacting them I also learned that the description that is floating around the net about the cleaner being an abrasive polish is not true. Neither the cleaner nor the polish are abrasive polishes. The cleaner is simply more aggressive in dissolving various organics generally described as dirt. But you can't use either if you actually need an abrasive polish such as after a final paint coat.
Meguiar's ScratchX, which according to info I found on the 'net is silicone-free, is not, at least not ScratchX 2.0. Their service confirmed to me that it contains silicone. They didn't answer my followup question about how they dare label it as "safe to use in a paint shop", which they do on their website.
In any case, their lie on the website seems to be the root of some people posting around the 'net that it is silicone free. It's not. Yes that explains the bare spot on my nitro refinished Ibanez Blazer neck
