Though such cells can be potentially dangerous. Li-Ions are not as inherently safe as NiHM cells. It's best to avoid 18650s and other Li-Ion rechargeables until one is fully knowledgeable about the dangers of such cells, and how to reduce that danger so that the lights which use such cells don't violently vent with flame (basically, explode).
While CR123 cells can also vent with flame, following a handful of basic rules will greatly diminish their potential of venting with flame. Cross-balancing isn't an issue at all. Never mix & match cells. (A good volt-meter helps with that. And isn't prohibitively expensive.) Never mix & match old and new cells in the same light. Never mix & match cells from two different brands. Never mix & match cells that have been used to illuminate, with brand new cells that haven't been used yet.
The last two rules are:
1) Only buy Made in America or Made in Japan cells. No-Name, Made in China, CR123 cells are dangerous junk! Avoid at all costs! (No matter how temptingly low the asking-price might be.) They're just not worth it. If you want to save money on CR123 cells....
2) Buy online from a trusted online shop (Such as Lighthound, Bright Guy, or Optics Planet). Buy in bulk. And once again, only Made in America or Made in Japan cells.
My last bulk purchase was a Case (12) of Energizer CR123 cells from Lighthound. Cost was $16 and a few cents. Compare that to $9 for just one Energizer CR123 cell at any Brick & Mortar pharmacy store. What I spent on those 12 cells online would not even be enough to buy two CR123s from a physical store.