I've used the client registration/login feature to qualify access to some galleries. Seemed a reasonable way to solicit contact details in exchange for access to more content. Problem is that i was getting quite a few [email protected] type nonsense email addresses.
Would really like to have the, relatively common, capability for an email to be immediately sent to the nominated email address with an included validate link. Would also then want a further automated email confirming registration. If I've attracted someone to my website and they click past the relevant landing page then i want their contact details before allowing access to further content. If they abandon at this point that's fine. If they're interested enough to supply contact details, email specifically, then i can work on offers or something to entice them further.
All of these add points that make my analytics more valuable and add useful capability to my marketing strategy.