Particularly pertinent for people trying to repair broken keyboards, the MSDS sheets for the rubber the keyboards are made of are posted here:
Some background information:
First, please note that silicon is a chemical element, and in pure form, such as in solar cells (or ICs), it is physically rather like dark grey opaque glass. It's brittle, and can break, like glass. You might compare it to coal.
Otoh, there are silicones (please note the final "e", which makes a lot of difference!) These are a family of compounds of silicon. To quote the Wikipedia article on silicones,
Silicones are polymers that include silicon together with carbon, hydrogen, oxygen, and sometimes other chemical elements. They can vary in consistency from liquid to gel to rubber to hard plastic.
Going to Wikipedia about [glue], one is redirected to Adhesives. In industry, what one might use to repair silicone rubber is a silicone adhesive. To some people, such as luthiers (makers of bowed and plucked string instruments), glue is animal glue, and the rest are adhesives; popular usage, of course, refers to adhesives as glue.
The type of silicone adhesive that seems by far the easiest to get is RTV (room-temperature vulcanizing) silicone. RTV silicones can be one-part, like tubes of gel available at retail, and two-part, used for making molds and encapsulating.
It cures ("vulcanizes") by emitting acetate [groups] (chemically speaking) which form acetic acid when combined with moisture.
This acetic acid attacks copper, which means that common silicone adhesive/sealant cannot be used with fine-gauge copper wire. It probably also attacks copper foil, so, most unfortunately, its use seems risky for repairing the silicone overlay of the XO keyboard.
There are industrial RTV silicone compounds that do not emit acetate (methyl, instead?) and do not corrode copper.
It's likely that almost nothing else will adhere to silicone rubber; probably the only useful adhesive is non-acetate-cure RTV.
A Google search on [RTV silicone adhesive non-corrosive] yielded a number of promising hits; following up on one revealed, for instance, LOCTITE SUPERFLEX NON-CORROSIVE RTV CLEAR SILICONE ADHESIVE SEALANT (no stock number given). Loctite isa very reputable company, and probably not the only one to make non-corrosive RTV.
It's very likely that any silicone adhesive described as electronic grade will not be corrosive to copper.