Will IPv6 help form-spammers?

A large (the major) part of developing a web application is to make it abuse-proof, more specifically spammer-proof.

I've just noticed that today's spambots manage to request a form, fill it in, submit it, and re-submit it (e.g. in case the CMS asks for more information before actually taking in the form data)... all from different IPv4 addresses.

First, two side questions:

• What techniques do they use to route different requests belonging to the same session (form submission) via different IPs, all within seconds?
• I could code a IP-based hash to check that the IP requesting the form and the one submitting it are the same; but: is there a legitimate reason why a user (i.e. not a spammer) might want to submit the form from a different IP than the one that requested it?

Then, to the meat of this question:

With its practically limitless number of addresses, will IPv6 make it easier for spammers to make webmasters' and web application developers' lives miserable?

Maybe end users will all have their own, static IPv6, which is a good thing for us because we can more easily block users whose machines are compromised.

Or spammers could continue to attack us from different angles, never using the same IPv6 twice... I am not too sure how it would work technically, especially since I don't even understand how it works with IPv4.

Question asked more or less on the day when IPv4 addresses are exhausted at the top level.