All 0.03% of the PS3 population are saddened by this.
Regarding advertised features and the EULA, I'm sure it's stated in there that features may be added and removed.
As for what SV said, that isn't true. Sony has supported Linux, and homebrew, ever since the original PSX regardless of piracy. Their support wasn't to preempt piracy, otherwise they would have just let people install Linux to begin with. Instead, they not only supported Linux, but they also provided full developer documentation for the hardware and APIs.
PSX had the
Net Yaroze, PS2 had the
Linux kit, and the PS3 basically had Linux support built-in. You could develop software specifically for the PlayStation hardware with each of these.
The PS2 and PS3 (I'm not sure about the PSX) run through a
hypervisor which restricted access to certain hardware components.
For the PS2, access to the DVD drive was blocked, but you could freely access everything else, including the graphics hardware.
For the PS3, you can access pretty much everything except the graphics hardware (this is due to a restriction placed by nVidia).
So as far as security with Linux goes, there's really nothing you can do to exploit the PS3. If there are security flaws in Linux libraries and such, you'll be able to exploit Linux to the fullest, but the hypervisor will still block access to the hardware itself.
However, these are separate from hardware bugs. If you've ever read processor
errata for any processor, you'll see that there are plenty of bugs and flaws within the processor itself. Sometimes they can be pretty severe. From what I understand about the PS3 exploit discovered not long ago, they are taking advantage of a processor bug with the PowerPC architecture. The person that discovered it said that it should work on other systems that use the same kind of processor, like the Xbox 360 or the G5 Mac. They can exploit this regardless of whether Linux is present or not.
I think there's probably two main reasons why Sony would want to remove Linux support.
1) While Linux cannot be used to exploit the PS3, if they do use the processor bug above, it may open up the full hardware for use in Linux, including the graphics processor which is under lock and key. If the system is exploited, you still won't be able to launch and run PS3 games from Linux. I believe they're just trying to protect access to hardware.
2) They need the room in the firmware. Firmware is a limited space. With the PS3 Slim out, they no longer have any use for Linux support in any future firmware update. By removing Linux support they'll free up a lot of room in the firmware for future updates.
Linux won't be the first feature removed from the PS3. PS2 backwards compatibility was promised and touted as a major feature of the PS3. That got removed some time ago. There has been no legal fallout or anything because of it. PS2 BC support is a million times larger than Linux support. People may complain now, but in the end no one will care.