While it doesn't take a rocket scientist to figure out what's happening here, it takes a bit more than connecting the dots to make a legal case stick.
[EDIT] Just to be clear I'm certainly not a fan of this. It strikes me as unethical and a little low on the "sleazy marketer" scale. I don't however beleive that this is illegal unless you can somehow prove that JillSmith03@gmail.com is professionally connected to AirBnB, and that this was done under corporate directive.
It's actually very easy to prove, because the same email was sent from several different accounts: you go after AirBnB directly and shoot for discovery, get them under oath to answer whether they did this or not.
If you have ever been questioned under oath, you know how tough it is to lie (ping me offline for details).
No point in chasing the gmail accounts themselves, that would be a dead-end.
While it doesn't take a rocket scientist to figure out what's happening here, it takes a bit more than connecting the dots to make a legal case stick.
[EDIT] Just to be clear I'm certainly not a fan of this. It strikes me as unethical and a little low on the "sleazy marketer" scale. I don't however beleive that this is illegal unless you can somehow prove that JillSmith03@gmail.com is professionally connected to AirBnB, and that this was done under corporate directive.