JohnSwanda Loc: San Francisco

Several responses now seem to have ignored that doing all your editing in PS on layers is nondestructive of the original, and can be changed at any later time.

russelray Loc: La Mesa CA

Any program can be destructive if one doesn't learn how to use it. Heck, Lightroom can be destructive because it way too often loses photos from its library.

DirtFarmer Loc: Escaped from the NYC area, back to MA

Point taken.
I was considering "destructive" to refer to the original file.

DirtFarmer Loc: Escaped from the NYC area, back to MA

True, you can preserve the original in a layer.
But PS does not HAVE to use layers, so the layer with the original image could be modified.
If you save an edited image from PS to the same filename, in the same format, in the same folder, the original will be destroyed.

As many people have noted, taking the proper actions will preserve the original in PS. Some actions will preserve the original image file and some actions will preserve the original image in a layer of a PSD.

If you flatten the image in PS, you remove all the layers. And a lot of people flatten their files because they can get pretty large otherwise.

DirtFarmer Loc: Escaped from the NYC area, back to MA

I don't recall that any of my copies of LR have lost any of the photos from the library.
I have fat-fingered problems occasionally, but they're problems with me, not LR.
I believe that once a library was corrupted, but a recent backup of the library enabled me to continue working with only a day's loss. And I can't blame LR for corruption of a file. It's more likely to be a computer problem or the action of the operator or a power glitch.

nadelewitz Loc: Ithaca NY

It is perfectly reasonable concept to do editing on a COPY of a photo file, rather than "tampering" with the original.
That way you don't have to wonder what your editing program is doing/not doing, as is evident from the responses, and if you mess up entirely in any way, you always have the original to go back to (and make a new copy).

This could be considered "common sense". Why discourage the OP from doing it?

CHG_CANON Loc: the Windy City

Fortunately, our OP " ..... but I have Lightroom and it is nondestructive .... " knows and understands more about the issues and software tools than many of the respondents ....

DirtFarmer Loc: Escaped from the NYC area, back to MA

Because it's not always necessary and making a copy of everything fills your disk twice as fast.

A better process would be to understand when it is necessary to make a copy and when it isn't.

via the lens Loc: Northern California, near Yosemite NP

Because he uses LR and it is simply not needed.

lamiaceae Loc: San Luis Obispo County, CA

Yup. It is just that a lot of people it seems do not know the difference between SAVE and SAVE AS. I don't have Lr and I destroy nothing with Ps CS6.

tommystrat Loc: Bigfork, Montana

LOL!

patman1 Loc: Pataskala, Ohio

I agree with you 100%, if you learn the basic fundamentals in working with PS you will never destroy an original.
NO. 1 all my photos are shot as Raw images
NO. 2 all photos are worked on copies only
No. 3 all work is done on layers
No. 4 Final copies are Save As, renamed and placed in its final location
Following these procedures as spelled out in the Adobe instructions as per the use of PS are quite clear. So my suggestion is to sit down with a manual and learn proper proceedures.

I am an expert in PS, been using it since its inception, PS 1, I believe it was about 1975. I also worked for for one of the largest Advertising Agencies in the world, DDB WORLDWIDE and these procedures were adhered too exclusively. LR was not used at all, it's really not meant for Advertising, more for Weddings were treatments can be made globally across many images.

mwsilvers Loc: Central New Jersey

Yes. And I understand about smart objects as well. I should have been clearer in my comments. Generally any image software that saves its edits permanently to the image file being edited is destructive editing. Non-destructive editing only applies edits permanently to exported or output files, not the originally edited files.

DirtFarmer Loc: Escaped from the NYC area, back to MA

I can't claim to be an expert in PS, only been using it for about 15 years.
1. I shoot raw only when possible. I don't have that option with my iPhone or with some modes in my D4/D5.
2. I guess all my original files are copies. The original was on the camera card and that has been reformatted. Additional copies are in my archives.
3. 90% of my work is done in LR, 10% in PS. The PS work is probably 70% layers, 30% single layer. But since the file has been sent to PS from LR, the original copy is preserved. All my image work in PS comes from LR. An occasional graphics piece will get generated in PS directly, but those things are specialty items for me and don't usually go into LR.
4. My PS work is saved and returned to LR. It uses the same name since I place useful names on my original copies at download time. The PS file is saved as psd, and shows up in the LR catalog, so I have both the original raw and the psd I can work on separately (in the rare case that any further work needs to be done). As far as the final location is concerned, that is the location saved in the LR catalog. If I need another copy for some other purpose I export it from LR.

nadelewitz Loc: Ithaca NY

The old saying is..."Better safe than sorry."
In addition, if the original file is stored an another hard drive, you are protected from loss, as with any other important data.