I am sure the Altassian / Trello team thought they had a good business reason for limiting user accounts to ONE email. However, in doing so they weakened Trello as a central repository for a person's daily activity.
One person multiple activities
The Trello board system is fantastic. It allows one person to have multiple boards serving different spheres of activities. A person might have a personal board, a board for his Scouting volunteer work, a board for his Kid's sport team, and a board for his job. His work might even need multiple boards.
One person, multiple identities
Managing these activities often requires having multiple email identities, or another way to look at it, channels of contact. Tying each board to a specific unique identity allows for interaction between the board and the email in ways that a single, global email can prohibit. Having a single master email makes sense for Trello business email, but not for how boards and email and other snap-ins interact.
Free accounts versus revenue accounts
It may be that this will become a paid feature. I hope that it is restored as a free feature. I fully support Trello paying its bills and making a profit. At the same time I believe this was an important aspect of Trello that allowed me to connect my Trello account to other apps by board. And perhaps Trello extensions to popular apps like GMail will be updated to solve this problem another way.
