Here's my take on this subject. Sorry for the long post ... but it's based on years of observations and mistakes.
Failure/lost images:
I shoot weddings and events ... sometimes up to 10 hours continuous shooting using 2 or 3 cameras ... including my MFD H3D-II/31.
Unlike many of my commercial shoots, there are no second chances if a disaster happens. A commercial job you catch in time to re-stage/reshoot, a press event, journalism/sports coverage, or wedding shoot is a one-chance, one-time gig.
Over the years, I've tracked CF cards disasters on various wedding & event photography sites. A vast % of those are due to user error, not the cards themselves. The cards CAN and do fail occasionally ... but the overwhelming % is user screw-ups of all kinds.
(I may take heat on this, but of the CF failures themselves, a majority are Lexar being used in a Canon DSLRs. Just reporting what I've observed ... and this may simply be due to the popularity of Lexar and Canon, so the numbers are statistically larger.)
User errors, especially in the frenetic environment of a wedding/event shoot, are by far the most common source of lost images.
They range all over the place ... from shooting over a previously used card; reformatting a previously used card; overshooting a card and corrupting a file or worse; accidently miss-loading a card in the camera and bending the pins (rare); switching off the camera and extracting the CF before the buffer empties (common mistake); trying to download to a separate HD during the event; accidental deletions & lost folders; losing card wallets; misloading in a card reader or computer failure while downloading; screwing up the down loads, etc., etc., etc.
No matter how experienced or prepared, no matter how organized the shooter may be ... it still happens.
Almost ALL of these screw-ups were people touting the "don't put all your eggs in one basket" concept using smaller cards. In fact, I cannot recall a single instance of an 8, 12 or 16 gig CF card failure.
Those long term observations convinced me to:
1) to use a dual card 35mm DSLR camera;
2) use the biggest CFs available;
3) change it well before it is full (which happens far fewer times, if at all, using large cards);
4) never delete anything on the fly, do that in the browser later;
5) never, ever, ever reformat on the job;
6) Download the CFs to a separate desktop folder, and set the cards aside until multiple copies of the desktop folder that have been made on separate HDs;
7) make sure your back-up battery is working ... and use dedicated, separate back-up batteries for your computer, your HDs, and your monitors if using 2 display monitors;
8) dedicate cards to a specific camera and mark it on the back of the CF.
On the subject of speed:
I use the fastest CF cards available from Sandisk ... Ducati or IV for 8 gig CFs, and IVs for 16 gig. When Sandisk gets around to 32 gig, I'll use those in my MFD cameras. I save all my older, slower CFs for goofing off in the studio.
I use 4 Lexar daisy chained stacked CF readers and download 4 cards at once to one desktop folder (they come with the short FW cord to link them together.) Lexar now makes these in FW800 which are "supposedly" twice as fast as my FW400 versions. Yes, you can download multiple CFs at once ... the computer doesn't care.
I occasionally multi-pass erase my CFs using the Disk Utility in Mac Applications, and reformat right away in the chosen camera. This cleans the CF of any latent, left over bits of data and junk that could currupt a file.
