(With reference to the Insights on 46b, citing Tosfos)
If there is a slight detriment to someone who benefits from an Eruv Chatzeros without his benefit, can we still consider this as an example of zachin ladam shlo bpnav or a rare case where we would say Chavin ladam shlo bpnav?
Steven Brizel
The RASHBA (Kidushin 23a) writes that in actuality, in most cases of Zechiyah, there is a slight Chovah, because one a person is Mezakeh something as a gift to his friend, there is a Chov of "Soneh Matanos Yichyeh" -- "One who despises gifts shall live" (and by giving a person a gift, one is causing him not to have this blessing). Nevertheless, the Zechiyah works.
However, what you write makes sense, and the Chovah in this case is more severe than the Chovah mentioned by the Rashba, and it is only because of the special dispensation of leniency which the Rabanan enacted in the laws of Eruvin that allows the Zechiyah to work here (as is implied in our Sugya).
Nevertheless, it goes without saying that in all cases, both Eruvin and normal gifts, if the person for whom the Zechiyah is being acquired refuses to accept it and reveals that his desire is not to acquire it, then retroactively the Zechiyah was never acquired for him (as the Rashba there explains).
-Mordecai