You can learn
about playing bass with the help of a computer. But I don't think it could *EVER* substitute having a real teacher.
That said, you might want to check out
www.musicdojo.com. It's an online music school run by adam nitti and a handful of other reputable teachers. They offer correspondence stuff with interactive audio lessons and readily available feedback and dialog with teachers and students.
So, it's probably among the best options for learning through the computer. Combined with a rigid an thorough practice regime, time and a love of music... you could certainly 'learn to play bass'
Many of the greatest bassists of all time were 'self taught', in that they didn't necessarily have specific music/bass teachers helping them along the way. They also didn't have computers or the internet. So how do you think they learned? They listened to as much music as they could, they saw as many live shows as they could, they practice as much as they could, and soaked up everything musically that they possibly could, then spit it back out at the world in the form of something new and awesome.
but... ymmv