To me, the permanent archive of all RSS feeds is far more important than the Google Reader front end. Critical comments that blog owners deleted on their site are still found in the Google RSS archive. In some cases it exposes true malfeasance, when blog admins change the comments of others. I can download whole RSS histories myself, but without a link to an independent archive my own copy is worthless as evidence, since I could have edited it myself.
You can limit the potential damage by publishing a hash precommitment of the archive; then later if you need it, you can provide the archive itself, let others verify that the hash matches the archive, and then any 'edits' could only have been made before the hash was made (which might have been many years ago, whenever an issue or scandal pops up which motivates a look into the archive).