Many have considered "friend-ing" someone to avoid having to seek consent or to avoid the cost of subpoenaing social media outlets and their users. This, however, is a dangerous proposition for those in the legal profession because the vast majority of states have adopted the Model Rule of Professional Conduct 8.4. Rule 8.4 makes it professional misconduct for any lawyer to engage in dishonesty or misrepresentation. The rule also makes it misconduct for a lawyer to supervise anyone in activity that would be misconduct if partaken by the lawyer. Thus, it would seem that "friend-ing" an opposing witness or even worse an opposing party would likely violate this rule (communicating with the opposing party would also violate Rule 4.2).
Additionally, somewhat related, the San Diego County Bar Association's Legal Ethics Committee dealt with a similar issue. There the lawyer sought to friend two employees of the defendant's company in hopes that they would let their guard down over social media. San Diego Bar Ass'n on Legal Ethics, Op. 2011-2 (2011). The committee rejected both arguments put forward. It determined that "friend-ing" a represented party is different than accessing an opposing party's public website, and it found that "friend-ing" is within "the subject of representation."
Model Rule 8.4 is by no means, the only ethical rule potentially implicated when an attorney seeks to friend a witness or opposing party. Model Rule 4.1 requires that in the course of representing a client that the lawyer not knowingly "make a false statement of material fact to a third person." The rule prohibits misrepresentations that "occur by partially true but misleading statements or omissions that are the equivalent of affirmative false statements." Since a material fact is one that could influence the listener, the act of omitting the purpose behind the friend request could prove to be a violation of Rule 4.1.
Further, Rule 4.2 provides an obstacle for this behavior. Rule 4.2 states that: "In representing a client, a lawyer shall not communicate about the subject of the representation with a person the lawyer knows to be represented by another lawyer in the matter, unless the lawyer has the consent of the other lawyer or is authorized to do so by law or a court order." There is nothing to suggest that this rule does not apply to electronic communications. However, an argument can be made that "friend-ing" is merely accessing public information, which is not prohibited by the rule. For instance, if the opposing party runs a website, there is nothing prohibiting the opposing attorney from perusing that website.
Model Rule 4.3 seems to address the attorney "friend-ing" a third party witness. Model Rule 4.3 requires that a lawyer, in "dealing on behalf of a client [,]" ensure that an unrepresented party understands the lawyer's interests in communicating with that person and must proactively clarify misunderstandings that the party may hold. Here again, it is likely that an attorney or his agent would have a duty to inform that they are not merely a neutral third party.
Many view the "friend-ing" of an opposing party or witness to be similar to an undercover investigation. In both instances, the attorney is placed in a situation where "misrepresentation" is certainly more likely and perhaps key to obtaining information. The difference though is that in a criminal investigation the ends are thought to justify the means. Several states including Alabama, Alaska, Florida, Iowa, Virginia, and Wisconsin all have modified Rule 8.4 to create a prosecutorial exception. In these instances, it is ethically acceptable for an attorney to supervise an undercover operation. Outside of criminal investigations however, misrepresentation only seems excusable to prove civil rights violations and to investigate intellectual property infringement where the agent was merely observing normal business operations of the target.
As things stand, there is no hard answer to whether a lawyer may make friend requests or have his agents do so. It lies on the fringe of many of the rules. Generally, the account from which the request is sent must be valid and truthful. Further, the greater the public access to the profile on which the information is contained the greater chances that the behavior will be deemed ethical. Greater public access makes the behavior of "friend-ing" more like observing someone in their ordinary course of business. For instance, Facebook may be joined by any member of the public and is thus more likely acceptable. If the networking website is typically reserved for certain groups, the requesting individual, attorney or agent, had better be properly includable in that group to avoid misrepresentation.
Finally, there is little to prevent a client from accessing others accounts. In other words, clients can friend individuals in an effort to conduct an investigation and then pass that information onto their attorney. An attorney can even passively use their client's login credentials to access information that the client would ordinarily have access. But an attorney cannot direct their client to provide messages directly to opposing parties.