Several companies are starting to release boot loader unlocking tools. This was done in response to the android community nagging manufacturers over and over and over again. The point of unlocking the boot loader is to make it easier to flash custom roms and to further push the capabilities of the device. Sony was one of the companies to finally respond by releasing an unlocking tool to the public.
Even though Sony has released the tool to the public and in doing so, seems to be saying they support the android developer community, they will not help you out if anything goes wrong with the device. The reports come in from XperiaBlog, where many users are stating that Sony has shot them down in attempts to have their devices fixed. Even with issues that have nothing to do with hacking, such as a yellow screen, are being rejected if the boot loader has been touched.
Now, Sony itself says that the warranty may be void if the boot loader is unlocked, so their response shouldn’t really be a surprise. Lack of support really does just come with the territory when you talk about hacking the device. So if you’re really wary about such things, you should probably at least wait till your manufacturers warranty expires before you dive in.