It was discussed at the first Ubuntu 14.04 virtual Ubuntu Developer Summit about enabling SSD TRIM by default for 14.04 and as of this week it's finally happened.
The Linux kernel has supported ATA TRIM since the 2.6.33 kernel and support has also arrived for major Linux file-systems like Btrfs, EXT4, and XFS for handling TRIM requests. Supporting TRIM requires setting the discard mount option for using TRIM when deleting files as it's not enabled by default. TRIM lets the solid-state drive know that a set of blocks are no longer being used by the system and can be wiped.
SSD TRIM benefits have long been known, but Ubuntu kernel developers finally decided on enabling the feature for its benefits after carrying out enough testing. SSD TRIM is enabled right now for the Ubuntu 14.04 development desktop but will be coming to Ubuntu Touch images too.
News of Ubuntu 14.04 finally enabling TRIM was made by Martin Pitt's Google+ page, "Finally, SSDs are now being trimmed automatically out of the box. Embarrassingly late, but at least in time for 14.04 LTS."