I could have used SD card?!?

I have stayed away from SD cards (in my projects) because of two assumptions;
1) They require difficult and fast SD control hardware and software, and
2) They're unreliable pieces of s***.
2B) It is possible that I have heard at one point about licensing required and thus (subconsciously) didn't even bother. But I'm not sure so this doesn't really count.

Only now I found out, almost by accident, that SD cards have SPI mode. I love SPI. It's dead easy to implement even in software, allows many devices to share a bus (kinda-sorta) and is very reliable. So if I, all this time, could have just put a SD socket on board and instantly gained huge amount of nonvolatile memory... Daaaaamn.

But point 1) still kinda-sorta stands. If I would need to implement FAT filesystem (instead of treating it as raw bulk storage), that would still take some software to do. At the moment I'm kinda struggling with current product line as I'm almost out of program flash, and there is still years of development to do. Even few kilobytes more would make my life very difficult.

But if could treat it as a raw storage. Instead of "small" SO8 flash chip (of just 16 or 64Mbit or so), SD card could be put there with more space than I could ever use. For my current purposes even 2 GB card would be nearly unlimited.

Did I mention I still like to program small? I just checked - Google home page is over 200kB, excluding any pictures (like the logo). That's just a bit less than program area of the current MCU I use, and it is packed full of functionality (the MCU, that is). Data structures I transmit over web (between devices) are few hundred bytes each. HTTP headers are often larger than that! So, comparatively, essentially unlimited storage.

But then we get back to point 2). Failure mode of flash memories is notoriously bad. At least early SSDs had habit of suddenly going completely inaccessible. One moment it would work fine, no issues, the next -- nothing. You couldn't get anything out of it. 
SD cards have similar track record, although being commonly removable, exact failure is harder to track, and might often be related to less than careful handling of cards.

I've dealt with those already mentioned SO8 flash chips. They may have "just" 64Mbit of storage or so, but they often promise something like 10000 erase cycles. That number is actually something I could trust - or at least believe.

SD cards, on the other hand, often seem to like to hide that number. There is this load balancer circuit that tries to hide that stuff from view, replacing it with meaningless "real world use" numbers for marketing purposes. 

But still. Take 2 GB memory card. Write, say, 512 bytes to it, every second. Let's assume that this specific card can tolerate only 100 erase cycles. This number, by the way, is highly conservative - even cheapest of the cheap flash chips these days offer at least 1000 erase cycles.

Even then this would mean more than 10 years of usable life for the product. Assuming, of course, that the balancer doesn't lose it mind in between and destroy everything. 

It's still very, very tempting...