I'm a software architect and also used to develop android apps in the past 2 years.
I'd like to point out a few things regarding these "mysterious" failures.
First of all, the reports are valid and affect a lot of Nexus 7 tablets and also a percentage of Galaxy Nexus devices built around 8/2012 to 11/2012.
However, this is usually not due to cheap or defective flash memory (from Samsung) but instead a bug in Samsungs flash controller firmware.
There are 2 known bugs - one actually could brick devices by overwriting protected blocks but allegedly has been addressed by Samsung - the other is frequently called "trim bug".
It begins to emerge if you fill your device up to a certain amount of free memory (roughly less than 3GB free). When the flash is low on blocks marked as "free", it starts looking for sections marked as "deleted".
The mentioned bug in their firmware causes that specific subroutine to run unusually slow and can lock up the whole device for several seconds.
Google rolled out an update for the Nexus 7 with Android 4.1.2 which doesn't fix the bug but avoids triggering it by actually removing data instead of marking it as "deleted" - so the controller is never running out of free blocks.
Unfortunately this doesn't help people already affected by the lags as afaik there's never been a "zeroing" of deleted blocks in the installation routine of the update.
Google also still hasn't included this fix in any of their Galaxy Nexus updates, which is quite questionable regarding numerous complaints in the google product forums.
I assume many devices out there and probably even Apple devices have this disfunctional controller if they are using Samsung flash built between 8/12 and 11/12.
However, this might never emerge as it's a combination of kernel fs module + flash controller firmware behaviour.
In case you have a Nexus 7 or Galaxy Nexus affected by serious performance degradation, I'd suggest the following:
1.) Verify the issue
Download AndroBench and run it, if your "Random Write Speed" is below 0,20mb/s, you're probably affected.
2a.) Resolve the issue on a Nexus 7
Make sure you are on Android 4.2.2.
Wiping does not help, instead fill your device completly with data and afterwards remove it again to "free" the flash blocks.
After a reboot the performance (AndroBench) should show better "Random Write Speeds".
2b.) Resolve the issue on a Galaxy Nexus
No easy solution known, but this is known to work well (I have 2 GNex, one affected and this suggestion did the trick):
If this didn't help, please check if userdata is mounted with the "discard" option.
To do so, install and start "Terminal Emulator", type "mount" and press enter.
If the line with /data doesn't have "discard" appended in the options, Google probably screwed up their fix by missing some device serials affected.