Quote from: azeteki on January 30, 2015, 05:22:28 PM

I think a better way to understand this would be to consider an orphaned block to have previously been a valid block, but no longer.

Terminology is important. A orphaned valid block never becomes invalid. Any client will see it as valid and that is not going change (one exception would be if another longer chain double spends the txn in the orphaned block).

However a valid block isn't all that matters. For a confirmation to have any weight it must be not just in a valid block but in a valid block which is part of the longest chain.

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If the longest chain is at 300K, and there's e.g. an orphaned block 200,001, at this point it's almost totally irrelevant.

True a chain which is 90K blocks behind the main chain is probably irrelevant but it isn't invalid. Invalid has a specific meaning in the Bitcoin network.

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Aside from curiosity purposes, the only reason I can think of to worry about non-main-chain blocks is very close to the tip of the main chain - it's possible that they have not made it in to the main chain yet.

Once again terminology matters. A non-main-chain block is never going to make it into the longest chain (unless the inferior chain becomes longer and thus becomes the longest chain via a reorg) I assume what you mean is that "it is very possible that transactions in the orphaned block may not have made it into the main (longest) chain".