I agree with Ariane. /v/ is not a labiodental consonant. In Latin there was a difference, but it began to disappear in the Middle Ages and disappeared in the XVI century. Mario has said that someone who pronounces /b/ and /v/ the same way may show signs of having a lower educational background. However, it's the opposite. People who pronunce them differently are in fact just trying to be too correct (or are influenced by regional languages or even by English). To me, it sounds as weird as if they pronounced the "p" in "psycology". And to support my comment, you can search "v" in the DPD (Diccionario Panhispánico de Dudas), which is elaborated by the RAE (Real Academia Española), the official institution that regulates Spanish. http://lema.rae.es/dpd/?key=v

/v/ and /b/ are pronounced exactly the same in Spanish, unless you're Julio Iglesias (sorry that's just a bad joke). /v/ is NOT (and has never been) a labiodental consonant. It's true that in some places in Spain its sound has been influenced by regional languages, and Indigenous languages may also have influenced its pronunciation in certain Latin American areas. However, /b/ is the official way to pronounce both consonants.

B with both lips. Ambos labios. v with superior teeth and inferior lip. Dientes superiores y labio inferior.

In certain areas in Spain, the difference between "b" and "v" is not taken into account, as Marina just commented, and this is mostly accepted. In America, on the other hand, we do follow the traditional phonetic rule of "b" and "v" (as explained by Daniel) which are the same in most languages using the Roman alphabet. I believe they are the same in Norwegian too. Now, many people will still pronounce "b" instead of "v" and the other way around, but this is generally viewed as mistake and it may lead a person to believe that the speaker has a lower educational background.

Yes. Actually there's a tiny difference between "b" and "v" in Spanish. Inside of Spain the variation resides in the region. For example, people who speak Catalan make the difference bigger because in their language is not really the same sound. Hope this answer was useful.