Actually, there are a couple of viewpoints on this. It is "illegal" according to the manufacturer. However, in the "same" light, you have purchased the machine, you are "not" making a "mod" to the software or operating system, it is simply bypassing the boot process.
Very technical, some view this as illegal, some view this as within your rights....... it is hard to base a decision on this. I can tell you that the manufacturer "DEFINATELY" says it is illegal, but you can go to the EFF.org and you will see that they view it as a legal mod........
Basically, the choice is yours....... If it is in warranty, any mod would void your warranty........ otherwise, I would say this is "fair game" and up to you individually.
I am a "firm" believer, with the "CHEAP" media that is used, and with normal every day use, that media becomes unreadable, thus I feel it is our personal right to make a "backup" for such occasions! Cheers! You will have to sort this dilema for yourself!