In my book I already discuss what the CFA is and whether you need or need not bother with it.
Here’re some additional thoughts.
CFA is really not something people on the sell side look for. I’m not sure exactly why. Maybe it’s for historical reasons. When you look at the sell side quants, very few have CFA.
That said, if your own educational background is not in finance — e.g., are you an engineer, computer scientist, physicist, statistician, or chemist by training (among other disciplines)? — than studying for a CFA serves three good purposes:
1. It gives you exposure to concepts in finance, even though many such concepts won’t be used by quants
2. It shows potential employers that you’re committed to pursuing a finance career
3. It allows you to pursue non-quant opportunities, after you gain some practical financial experience (BTW, here’s the catch-22, though: to get the CFA title you must have "relevant" experience in finance)
My take is, if you have a very strong quantitative background and have a good chance of landing a quant job (and esp. if you’re getting a Ph.D.), CFA is not necessary for either buy side or sell side. Otherwise, consider going for it; it won’t hurt.
Great tip: you don’t need to tell prospective employers you’re going for the CFA, unless you already passed at least one exam (namely, Level I). Otherwise, if you tell them and you don’t pass (just in case!), it’ll look a bit embarrassing, won’t it?