MacBook – Power for the US laptop in Europe

In general, extended warranty plans are a healthy-sized profit center for the company offering them. This implies that unless a product turns out to be less reliable than predicted, on average (mean average) customers will be better off paying for their own repairs without the warranty. However, if one can't afford to self-insure for abnormal or even normal deviations from the average, something like AppleCare will lessen the downside financial risks.

Thus, I suggest (and buy) AppleCare only if an Apple product seems to be getting numbers of reports of below average reliability (e.g. the Duo 2xx and PowerBook 5x00 product lines). For other Apple products, maybe put the money in a savings account instead, and there is a good likelyhood that you'll end up ahead after a decade or two of Apple products.

According to Apple, yes, it can carry power for devices in some circumstances. Specifically:

7. Does the Thunderbolt port supply power to connected devices?

Yes. A Thunderbolt port supplies power if that Thunderbolt port is part of a device that is connected to an AC power outlet or is operating on battery power. If your Thunderbolt devices have their own power supplies, you should connect the power supplies to them for optimal functionality. If you are using Thunderbolt devices that get their power only from the Thunderbolt bus, computers running on battery power will experience battery drain more quickly.

The Thunderbolt specs on the Wikipedia page for Thunderbolt currently say the copper-based version of the Thunderbolt protocol can deliver 18 V at 550 mA (9.9 W max). Presumably all Thunderbolt cables are built to this spec and can handle that kind of power passing through them. Whether the connected device can supply that kind of power is another question that can only be answered by looking at specific devices.

Thunderbolt over an optical, instead of copper, connection would not be able to carry any power with the data signal. I note this only because Thunderbolt was original designed to be an optical protocol; though its since been adapted to copper which is a good thing.