Wow great feedback, much appreciated!

I understand your concerns about the "Dead accounts" issue.
The best countermeasure against it, from my point of view, is to don't give any incentives for just referring an account alone.

As written in this post, it's required that the referred user is going to use HIVE as it's intended and bring value to the platform: creating quality content. Since a quality post can generate thousand times much post rewards than multiple low quality post - I can't think of any scenario, where creating endless accounts would generate any referral rewards at all.

I would agree, if a referred user would receive some-kind of welcome reward - which would ultimately lead to the referral spam you pointed out.

Really cool that you mentioned the idea of "tie" a user to his referral. That's exactly what I have done with @hiveonboard (but not announced yet).

If a referred user has created an account, I'am sending out 2 memos: 1 for the referred person and 1 for the referrer in order to create a connection.

Just check out the 0.001 transactions seen in here:
@hiveonboard/wallet