Yesterday, I just lost access to a btrfs partition.
I don't think of something that could have induce that.

I tried to remake the partition using diskdrake.
I had the message asking to format, and check for bad blocks (yes to both):
# mkfs.btrfs -c /dev/sda5
mkfs.btrfs: invalid option -- 'c'
usage: mkfs.btrfs [options] dev [ dev ... ]
options:
	 -A --alloc-start the offset to start the FS
	 -b --byte-count total number of bytes in the FS
	 -d --data data profile, raid0, raid1, raid5, raid6, raid10, dup or single
	 -f --force force overwrite of existing filesystem
	 -l --leafsize size of btree leaves
	 -L --label set a label
	 -m --metadata metadata profile, values like data profile
	 -M --mixed mix metadata and data together
	 -n --nodesize size of btree nodes
	 -s --sectorsize min block allocation
	 -r --rootdir the source directory
	 -K --nodiscard do not perform whole device TRIM
	 -V --version print the mkfs.btrfs version and exit
Btrfs v0.20-rc1

Without checking for bad blocks:
# mkfs.btrfs /dev/sda5

WARNING! - Btrfs v0.20-rc1 IS EXPERIMENTAL
WARNING! - see http://btrfs.wiki.kernel.org before using

No valid Btrfs found on /dev/sda5
Open ctree failed

I suggestion marke btrfs as EXPERIMENTAL in diskdrake, as I didn't know the status of it before I lose a partition....

Reproducible: 

Steps to Reproduce: