Observable.share() issue

observable-share-issue.ts

@Injectable()
export class AuthService {
  private user: BehaviorSubject<User> = new BehaviorSubject<User>(null);
  
  login(username: string, password: string) {
    let user = new User("username", "email");
    this.user.next(user);
  }
    
  /**
   * @returns observable with current logged in user or null if user is not logged in.
   */
  getUser(): Observable<User> {
    return this.user.asObservable();
  }  
}
    
@Component({
  moduleId: module.id,
  selector: 'navbar',
  templateUrl: 'navbar.component.html'
})
export class NavbarComponent implements OnInit {

  private user: Observable<User>;

  constructor(private _authService: AuthService) {
    this.user = _authService.getUser();
  }
}

@Component({
  moduleId: module.id,
  selector: 'user-profile',
  templateUrl: 'profile.component.html'
})
export class ProfileComponent {
    private user: Observable<User>;

    constructor(
      private _authService: AuthService,
      private _profileService: ProfileService) {
        this.user = _authService.getUser();
    }
}
    
both profile.component.html and navbar.component.html are using snippets like:
{{(user | async)?.username}}
{{(user | async)?.email}}
{{(user | async)?.otherField}}
    
If I change the method to:
  getUser(): Observable<User> {
    return this.user.asObservable().share();
  }  
    
Then behavior is very strange, one component doesn't see the values at all, second sees the username but email is empty, etc..
I think share makes sense only if you really subscribe to it, but in your example we simply assign observable to field 
and then use through (data | async) which may cause these side effects.