If you want to play a 11 string bass, go for it. It is certainly no skin off of my teeth. I've never understood why people have to "get" why someone would want to play more than 4/5/6/etc strings. Isn't the fact that they
want to enough? Apparently not...
I mostly play 4s and 5s now, but I've played 6s in the past before I finally acknowledged that anything wider than a 5 makes my hands go numb after a short period of time. I didn't think I was better when I played a six, and I don't think I'm any less proficient on a 5.
If you can groove on a 4, you can groove on a 9. How does a guitar player having the "responsibility" of playing chords mean that I can't play them on bass?

What a limiting mindset. At blues gigs, I'll sometimes play some minor chords during slow minor blues tunes while the guitar player plays a solo. Does that make me a wanker because I want to add some context, and color under his solo? Would I be more of a wanker if I was doing the exact same thing on a 6 string when the neck was 1/2" wider with an extra strip of metal from the bridge to the headstock? Is it appropriate for every situation? Of course not. But, then, I wouldn't spit blood or fire at a blues gig, either. Gene Simmons has no problem doing it at his shows, though.
Simply having more strings doesn't make one a wanker. Having more strings doesn't make someone a "frustrated guitar player." Having more strings doesn't mean someone only wants to solo up high. I've heard good bass players on an 8/9 string, and I've heard wanky bass players on a 4 string. There are still only 12 notes available.
People don't only play extended range basses because they want more notes. I don't only use the notes below E on my 5 string--do you? I like to stay in one position if I can--especially on 4 hour gig nights. So, if I can play an F at the sixth fret on a B string as opposed to going down to the first fret on the E string, then that's what I'm going to do.
Personally, I think less of a person who mocks a bass player for his choice of instrument than I do of a person who chooses an extended range bass for his tool of expression. Shouldn't we focus our energy on a group truly worthy of scorn?
Drummers.
EDIT: Here's a pic of Chuck Rainey playing Al Caldwell (plays with Vanessa Williams) 9 string. He really liked it and the possiblilities in opened up. Chuck has been known to play a 6 string bass. Any of you guys want to call Chuck Rainey a wanker? I thought not...
http://www.talkbass.com/forum/attachment.php?attachmentid=7837