I format my garden camera SD cards every morning, in the computer.
If you mean DLSR type cameras, then yes, format in the camera. But I never use the garden cameras to format the cards - don’t like using up the battery capacity - had no problems over the years. I need 12 lithium batteries in each of 3 garden cameras - pricy!
SD cards are very definitely electricity.
OK, yes but that’s a slightly different scenario. Deleting images using the camera UI should always be safe, assuming they were taken and stored by that camera, moving an SD card to a new camera - I agree that might not always work and reformatting a card in camera will always (unless the card is faulty) make sure it will work in that device.
But moving the card to something more generic such as a PC or Android tablet should not require reformatting.
You are of course correct - I was having a brain-fart late last night, remembering magnetic memory, rather than the storage of electrons.
General consensus is that, possibly due to poor programming on behalf of some camera makers, deleting images in camera is not OK. All evidence is anecdotal, with people reporting issues shortly after deleting images, but without incontrovertible proof. It may also be historical and now irrelevant, with more recent cameras much better and the memory they used more reliable than the older CF cards etc.
There was a discussion recently about using cameras with only a single card slot, with the professionals refusing to even contemplate such a flawed design. I’ve not ‘lost’ a card in the last 10 years, but before that had an SD break down and also one of those odd memory card designs from Olympus fail.
No need to, but I’d just reformat to remove the cruft that a camera adds if I were to use an SD card as a general purpose storage device. For the cards in question (used in a trail camera) then I’d not bother.
Many of the guys I ‘know’ would format the card each time they want to clear it of images, regardless of type, and that’s generally what I do. Most of my stuff takes plain SD cards, although my old D70 uses CF, and I try to rotate cards, keeping the last ‘full’ card to one side in case upload to the PC had issues that weren’t discovered during the first quick viewing of the images. Next card in the camera gets formatted before I start using it.
In the end it doesn’t matter as long as what you do works for you and you don’t lose anything.
I only use the extreme/ultra/endurance cards in cameras after too many failures do to high rewrite hours.
As a professional user of video cameras, I have experienced (I think) 4 card failures in about 15 years of use.
Losing your rushes is, of course, an unforgivable sin, so I only used cameras with dual slots, recording to both at the same time. Before we left each location, all files were backed up onto 4 separate external hard drives so we had the 2 original cards, plus 4 hard drives as backup.
Paranoid? Perhaps - but at least I never had to explain to the client that the essential footage needed was not available.
I have been a professional (digital) photographer for 20+ years, shooting with various different models of Canon, Panasonic, Sony and Fujifilm cameras, and have deleted individual images in-camera many times over the years with no issues.
I appreciate this problem may have actually happened to you, in which case fair comment, but on the whole I think it’s a bit of an “old wives tale”. The only time I’ve had an issue with image corruption on a memory card was one time when I took the card out before it had finished writing files.
I do generally format cards in camera, but that’s mainly because the camera is going to add its folder and file structure to the card when you insert it into the slot and turn the camera on, so formatting on the computer is fairly pointless. 
Again, speaking as one of those pesky professionals I do prefer to use cameras with dual card slots and have the camera write a backup to the second card, but that’s more as an insurance against physically losing a card or reformatting it prematurely than because I am worried about in-camera file corruption.
I also shoot “RAW plus JPEG” as extra insurance! 
What I do have is a very structured procedure for managing cards after a shoot - I keep all cards from a shoot in a small plastic bag labelled with the job name, and they don’t get formatted and reused until I have delivered all images to the client and archived the job. That’s overkill for amateur use of course, but I will probably still continue to use the system when I retire and am just taking photos for fun, as nobody likes that sinking feeling of realising that important images are gone forever…
I’ve had image corruption occasionally in the past, but that was unrelated to deleting images.
One of the guys on Talk Photography who seemed to know about file management and databases gave some good reasons why deleting images in camera could cause trouble. Seemed legit. I’ve deleted images when short on space and had no trouble, but also have no wish to find otherwise. I’d suggest that if you don’t HAVE to delete in camera then it’s probably best not to.
