Taking G-d’s name in vain appears to be a biblical transgression, as indicated by the Talmud (Temurah 3b, Nedarim 7b, 8b). However, the question of an unjustified berakhah (berakhah l’vatalah, or berakhah sh’einah tzrikhah) is a more complicated one. The Talmud (Berakhot 33a) connects such a berkahah to the prohibition of “You shall not take the Name of Hashem your G-d in vain” (Shemot 20:7). However in the view of some rishonim (Tosafot, Rosh HaShanah 33a and Menachot 67, s.v. zecher, Rosh, Kiddushin I, 49), and as interpreted and accepted by the Chazon Ish (O.C. 137:5), when G-d’s Name is in incorporated into a statement of praise, such as a berkahah, no biblical violation is incurred, even if that berakhah was unwarranted. Rather, the Talmud’s intent is that a rabbinical prohibition is violated (and the citation of the verse is an asmakhta.)

The position of the Rambam on this matter is debated. The implication of his statements in Hil.Berakhot (1:15) and Hil.Sh’vuot (12:9) is that a berakhah l’vatalah is biblically prohibited. However, the Chayei Adam (Nishmat Adam, klal 5, 1) and R. Shlomo HaKohen of Vilna (Resp. Binyan Shlomo, I, 20) disputed this reading and felt that the Rambam would acknowledge the above position.

Commenting on the Chayei Adam, R. Shlomo Zalman Auerbach (Resp. Minchat Shlomo, I, 18:9 and II, 3) suggests that the rabbis enacted the prohibition of berakhah l’vatalah in order to protect the institution of berakhot in general; if one were able to make berakhot randomly, at will, the actual obligations would become meaningless and appear arbitrary.

Nonetheless, many acharonim (see Magen Avraham 215:1) took the Rambam at face value to be saying that berakhah l’vatalah is a biblical obligation; as the footnotes to the Resp. Binyan Shlomo point out (p. 180, #1) the Rambam in his Responsa (Blau edition, #124) says so explicitly. (See also Resp. D’var Yehoshua, II, 27:25). [This opinion is vigorously challenged by the Satmar Rebbe (Resp. Divrei Yoel, Y.D. 85:3-5).]

R. Akiva Eiger (Responsa, #25) goes farther and understands from the Rambam that not only is a biblical violation transgressed when a berakhah l’vatalah takes place, but that that transgression is actually worse than taking G-d’s Name in vain. While the latter is actually an issur aseh, a berakhah l’vatalah is grouped with a needless oath, and both of those constitute actual prohibitions. Thus, berakhah l’vatalah is prohibited independently of G-d’s Name being unnecessarily mentioned, and is forbidden even if a substitute for the Name is used. R. S. Z. Auerbach (Minchat Shlomo II, 3) explains this position (after extensively questioning it): both oaths and berakhot are inherent invocations of G-d’s authority. Thus, even if a substitute for the Name is used, the intent is still to call upon G-d’s Name; and when this is done frivolously, a transgression has been committed.