Thanks laat2. I called Bosch today to ask about a replacement top, and they carry the Siemens top for my unit at a price of 640 plus labor. I have a Bosch tech coming out a week from today with the top. It's an expensive repair, but a new unit is $2,000+.

Does anyone know if there is a real risk of electrocution if I continue to use the appliance with the crack in the top?

I certainly won't tell you that your cooktop is OK to use (both because I have not seen it and because I don't want to be sued by your grieving family), but there is nothing mystic about this. Electrocution can only happen if you come in contact with an electrically conductive part that is not grounded (which includes water that is in contact with a metal part inside the cooktop). The fact that the glass is cracked makes it more likely that you, or spilled pan contents, could reach a dangerous part inside the cooktop, that is all. Manufacturers' instructions are generally very conservative.

I'd actually be more concerned that the cooktop could fall through the counter (they are generally held up by the glass resting on the counter). Cracks can sometimes propagate rapidly.

Caliente, thanks so much for your thoughtful (and funny!) response. I guess it's better not to risk either possibility, so I suppose I'll make friends again with my microwave and ovens. I hope the repair is possible and I don't wind up buying a new induction cooktop less than 3 years into my affair with induction. :)

Thanks!

The 'hob' is the counterpart of a gas cooktop 'burner,' except with induction a hob comprises more parts. In this case the most relevant parts are the glass cooktop where the hob coil is, the coil itself just underneath the glass, various bits of insulation, and (one hopes) whatever temperature sensor is embedded at the center of the coil. Other parts are the electronics controlling the coil, and the power supply modifying prime power and generating the coil waveform. The temperature sensor should have detected a blazing hot pan and shut down the hob.

Once the glass is cracked, and assuming that the coil and its circuitry are still capable of being powered, one has high voltage accessible without a sealed covering. As noted, almost any liquid being cooked could spill and run into the glass fractures, and most of these liquids will be sufficiently conductive to make a circuit connection to someone touching the liquid. At this point an electrocution hazard will be present. If another part of the person is grounded, even barely, a shock potentially causing electrocution is likely. Medium voltages at 40 kHz are definitely hazardous.

In addition, once liquid is inside the electronics, more can be damaged than just the glass top. I would put some paper towels over the cracks as protection against spashes, and/or seal the cracks with shipping tape, and de-power the unit using its circuit breaker or other disconnection means.

While this information may come in handy to someone in the future. The OP posted this over 6 years ago. I'm thinking they have most likely addressed the issue by now.