I'm using the alphabetic style of biblatex as follows:
\usepackage[
style=alphabetic,
maxcitenames=3,
minnames=3,
useprefix=true
]{biblatex}
In the .bib-file, I have an entry:
@article{opera,
author = {Bach, Johann Sebastian and van Beethoven, Ludwig},
year = {1760},
}
When cited, this article will be rendered as [BB60]. Since I set useprefix=true, I expected the von-part to be present: [BvB60]. Is this a bug? How do I get the desired behavior without explicitly setting the label=BvB field in the BibTeX entry? And why is false the default value for useprefix?

biblatexanduseprefix=true, I get "BvB60". – lockstep May 11 '12 at 4:13