.biz and .info etc

[temi]

Gentlemen and Ladies,
Is it worth pre-registering any of the above extensions or is
"pre-registering" a non existent domain extensions a  thinly disguised
rip-off?
Most of the companies offering such services are careful to promise you
nothing, nor do they promise to refund you money in the event that they are
unable to secure the domain for you. your opinions please.

Regards
Temi