Atlassian make it hard to avoid this
Atlassian have a history of merging accounts between personal and work - it's not that easy to avoid. I nearly lost all my personal Bitbucket content when leaving an employer because Atlassian had managed to combine my personal account with my work account despite me trying to keep them separate. I think it happened when they converted standalone Bitbucket accounts into Atlassian accounts, just as they're currently doing with Trello. Luckily I had a good relationship with the account manager at that company and managed to get it sorted out, but it took a while between us to figure out what we had to do.
All the people saying "don't mix work and personal" - it really isn't that straightforward to avoid with Atlassian, they link stuff up behind the scenes without being explicit about it.