In Canada

" In a fiduciary relationship, one person, in a position of vulnerability, justifiably vests confidence, good faith, reliance and trust in another whose aid, advice or protection is sought in some matter. In such a relation good conscience requires the fiduciary to act at all times for the sole benefit and interest of the one who trusts."

Instead of wikipedia, how about employing the language of actual court rulings.

In Frame v Smith (cited as [1987] 2 SCR 99), the Supreme Court of Canada stated:

"In the past the question whether a particular relationship is subject to a fiduciary obligation has been approached by referring to categories of relationships in which a fiduciary obligation has already been held to be present. Some recognized examples of these categories are relationships between directors and corporations, solicitors and clients, trustees and beneficiaries, agents and principals, life tenants and remaindermen, and partners. As well, it has frequently been noted that the categories of fiduciary relationship are never closed.
"Relationships in which a fiduciary obligation have been imposed seem to possess three general characteristics: the fiduciary has scope for the exercise of some discretion or power; the fiduciary can unilaterally exercise that power or discretion so as to affect the beneficiary's legal or practical interests; (and) the beneficiary is peculiarly vulnerable to or at the mercy of the fiduciary holding the discretion or power."(emphasis added)
In Ben-Israel v Valcare Medical, 78 CPR (3d) 94, 1997, Justice Beaulieu of the Ontario Court added:

"A fiduciary duty imposes the highest duty in law on the party holding the duty - the fiduciary - to act altruistically for the sole benefit of the beneficiary, to the fiduciary's own detriment if necessary. The traditional categories of relationship in which a fiduciary duty exists are agent to principal, lawyer to client, trustee to beneficiary, business partner to partner, and director to corporation. In all of these situations, a fiduciary duty exists because the fiduciary has assumed a position, and taken on a responsibility, in which the beneficiary's interest is dependent upon the fiduciary's actions. There are, however, other situations in which the duty arises, based on the particular situation and relationship of the parties...."
An important clarification was made by Canada's Supreme Court in EDG v Hammer 2003 SCC 52 where a majority of the Court agreed with Chief Justice McLachlin when she stated that:

"Fiduciary obligations are not obligations to guarantee a certain outcome for the vulnerable party, regardless of fault.  They do not hold the fiduciary to a certain type of outcome, exposing the fiduciary to liability whenever the vulnerable party is harmed by one of the fiduciary’s employees.  Rather, they hold the fiduciary to a certain type of conduct.
"(A) fiduciary is not a guarantor.  A fiduciary does not breach his or her duties by simply failing to obtain the best result for the beneficiary”.

Now, Patrick, please read especially the criteria established by the Supreme Court of Canada, which I have emphasized by bolding, above. Do you think that reliance upon a bulletin board post meets those three criteria?