Added fraud proof motivation.

bip-codeshark-jl2012-segwit.mediawiki

@@ -29,6 +29,9 @@ By removing this data from the transaction structure committed to the transactio
 #* Size of witness could be ignored / discounted when calculating the block size, effectively increasing the block size to some extent
 #* Hard coded constants, such as maximum data push size (520 bytes) or sigops limit could be reevaluated or removed
 #* New script system could be introduced without any limitation from the existing script semantic
+# '''Additional data required for fraud proofs can be added to witness'''. Extra data can be committed that allows short proofs of block invalidity that SPV nodes can quickly verify.
+#* Backlinks for the outputs spent by the transaction's inputs can be provided. These backlinks consist of a block hash and an offset that thin clients can easily query and check to verify that the outputs exist.
+#* Sum trees for transaction inputs and outputs can be committed making it possible to construct short proofs that no new coins are created in any noncoinbase transaction and that the miner does not add excessive fees to the coinbase transaction. 
 
 ==Specification==