Aaaaargh!!! So pissed off right now since I've just realised I sold my PS3 (to get a newer one) and forgot to copy my save data to a memory stick before deleting everything - most of it was fine, except I've lost my FFXIII data and won't be able to Platinum the game anymore!... thus inspiring this thread.
Same sort of thing happened before when the YLOD struck my old 60GB and I lost Motorstorm 2 data (I needed 3 more gold medals for a gold trophy!) and GRID data (I was on the last race to complete the game!) amongst others.
Probably the most annoying of all was when my GBA ran out of battery just as Pokemon Emerald was saving. The data was corrupt and nothing was salvaged... I must have lost 10+ level 100 Pokemon and played for over 100 hours. I found it hard to get out of bed for months mornings afterwards.
FML... My venting's done, I wouldn't mind hearing some more stories just to see I'm not the only one (actually, I know I'm not, I've seen YouTube videos)... Have you ever had saved data deleted/go corrupt when you spent so long or worked so hard on a game?