With a larger block size, the long-term cost to the network rises.
Each kB of block chain must be stored by all of the full nodes participating in the network forever, given the current system.
Each kB of transaction stored in the chain has a very real long-term "cost".
The increased cost is permanent.
Speaking of this, there will be a -prune option in 0.11 (stable version should be out soon, currently in rc2) that allows you to autoprune the old block data with wallet disabled.
https://github.com/bitcoin/bitcoin/pull/5863Running a pruned node with wallet won't be included in 0.11 though.
https://github.com/bitcoin/bitcoin/pull/6057