Adding Business Category to the profile

1.  Business Domain/category as an additional field: Members provide their business domain category (example: DotSign could be under Internet solutions, Graphic design or so) - may be I can list myself in Multiple categories (but mus have some limit say 3 categories max or so). If someone doesn't  fit in anything then they can email the admin who can add a new category if it makes sense.
Why we need it. current profiles helps to know who is who, but when I am looking for some one in our group with reference to a specific need, its hard to go through every ones profile 1 by 1 to know what they do.