Yes, this is possible. The last hop will fail the payment because it won't know who the next hop is supposed to go to.
What is more common is to have the payment hash be set to a random value so the sender knows for sure the payment will fail. This is called "probing" and people do it to figure out if a payment for a certain amount will work on a given path.
It's VERY spammy at the moment, something like 90+% of payments over lightning are currently probing attempts that fail (on purpose).
Wow, more than 90% sounds sick. Are there any attempts to prevent this, or is it intentional?
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Yeah it hasn't been too much of a problem so far. It might be more than 90% honestly. I've seen some reports of 99%.
I'm not actually too versed on potential solutions but I think it will need to be addressed at some point. I know there are a couple competing ideas people are arguing about trade-offs over but no obvious solution at this point.
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