This question is a bit of side topic from this thread. While there is no problem with people viewing deals without signing up for an account, there are loads of benefits of signing up.
So the question is why did you sign up? What things can we do to encourage more lurkers to sign up?
My personal story is that before OzBargain, I used to find all my freebies and deals from Whirlpool's Freebies threads. Scott used to post there and I think either him or someone else linked to the OzBargain Blog. I followed that for a while when eventually he created OzBargain. As a natural progression of commenting on the blog/Whirlpool, I signed up for an account.
Free stuff..