Yes, they can. In fact everything in the chain can fail; switch, DC power supply, and laser. Good news is that all 3 components are "easy" to replace
Bad news is that if you want exact OEM components they are ridiculously overpriced and often hard to find
More good news is that you don't need insanely overpriced OEM parts
I also have a Delta Twin Laser 12" and would argue that's its one of best implementations of laser guides ever built into a saw. I've read many posts with users soured on laser guides because many of the other systems really are only for rough alignment. The Delta Twin was done right
Anyway, mine failed about two year ago
and wow beyond wow I really missed it. I liked it from day one but didn't realize how dependent I had become on the super convenience of it. In my case the power supply had failed.
I found an authentic OEM replacement from an online source but it was $75
RIDICULOUS
I went to Radio Shack, picked up a clearence power supply for $7, ripped the guts out of the little case, and put the module into the saw. Its been fine since then.
If the lasers ever fail, you can find compatible sized modules on e-bay for a few dollars. I considered swapping out the red units for green ones but decided "if it ain't broke ... don't break it" but its an option for the future.
The switch may be a little harder to track down if you want an exact replacement. Worst case, I would just drill a new hole in the plastic housing in an "open" location and install a simple mini toggle switch or push button. Maybe $2 - $3 max., certainly would never pay $47 for an OEM model. Another option would be bypassing the switch completely and having the laser powered all the time. THEN, putting a switch on the main power cord and just turning the entire saw "off" when you are not using it. Or just unplugging it.