The difference is Linus won't take your arbitrary data and persist it in the kernel's history and Bitcoin will for a small amount of money. This makes some interesting schemes possible to implement: timestamping, proof-of-existence and similar services. For example Keybase.io uses Bitcoin like that to prove that are not messing with people's data [0]. Another interesting use is creating virtual tokens via Counter Party [1].

If you don't want to pay you also "abuse" Certificate Transparency logs to do basically the same job, just like Mozilla with their Binary Transparency [2].

[0]: https://keybase.io/docs/server_security/merkle_root_in_bitco...

[1]: https://counterparty.io/

[2]: https://wiki.mozilla.org/Security/Binary_Transparency