Account lockouts

Does stuff like account lockout get accepted for a pre-registered user, Considering when you invite someone, It sends a notification and an activation link to their email, and if that user was to ever be invited into someone's company that he actually belongs to, He will only get a notification with no way whatsoever to activate his account.

I imagine at a large scale (say an email database with 1 Million emails), It'll be a major problem and a revenue loss for the company, What do y'all think?