My answer is that whatever transactions the miners choose to include in the blocks have sufficient utility to be included.
This should follow real supply and demand for block space, not an arbitrary blocksize limit. The blocksize limit should be continued to be used as an anti spam measure which should exist significantly above the current average transaction volume.
So if I decide that my posts should be included on the blockchain, and a miner decides that a few Satoshi will reward hie enough to include them in a number of blocks, then that will be of benefit to Bitcoin. Even though every node will have to store them forever.