I missed let in front of talk:
<div *ngFor="let talk of talks">
Note that as of beta.17 usage of #... to declare local variables inside of structural directives like NgFor is deprecated. Use let instead.
<div *ngFor="#talk of talks"> now becomes <div *ngFor="let talk of talks">
Original answer:
I missed # in front of talk:
<div *ngFor="#talk of talks">
It is so easy to forget that #. I wish the Angular exception error message would instead say:
you forgot that # again.