OK, let's not get too carried away! :eek:
The AD-7240 series and the AD-7260 series share the same hardware and it is even possible to crossflash between the two, so it is quite normal that they are identical.
The AD-7280 series uses a different (NEC) chipset than the previous two series, so a crossflash is impossible.
Regarding the apparent external similarity between the LiteOn's and the Sony Optiarcs, if you look at the belly of the drive you'll notice that in fact there are some noticeable differences.
Just because two drives made by two different manufacturers, look the same on the outside, and share similar or the same tray mechanism that doesn't mean they will be the same on the inside! One of the drives is based on a Mediatek chipset while the other is built around a NEC chipset, both completely different in functionality and software/hardware architecture, as well as in capability and features and made by two different companies (which in spite of whatever partnership they might have are still competitors). It is not a matter of the two chipsets being somehow equivalent so you can replace one by the other with minor hardware/software modifications.
If you open the drives and compare the inside electronics you'll see that they are indeed very different. The firmwares they use are structurally different too.
In conclusion, just because the two companies might have some sort of partnership and might share some of the mechanical drive infrastructure (presumably because they want to share some manufacturing and/or research/IP costs), that doesn't mean the drives are the same... the tray and case used may be made by the same company (whichever that might be) but this 'shell' aside, we're looking at completely different 'cores' - which at the end of the day is what it really matters.