I bought chicken breasts at whole foods in Friday night. Marinated them that night in lemon and lime juices and olive oil. I never cooked it.

I don't mess around with raw chicken. They might be safe, but why risk it? 4 days is a long time to store them uncooked. Next time you don't have time to cook chicken, throw them in the freezer, marinade and all. You could always turn them into chicken salad, even if the marinade is too tart, as Sam said.

TOSS!

Should be safe...but I'd bet they've way over seasoned with the citrus and mushy as mentioned.
I'd probably cook them and make chicken salad.

I'm in the fine to eat camp. It depends on how long it was at whole foods, and how cold/airtight you kept it during the transport and marinating process. Assuming you kept that safely, chances are good that it's totally fine. That said, as pierino suggests the texture may be off because of the citrus in the marinade.

If they were refridgerated overnight they are probably okay. The lemon and lime retard spoilage. But in all likelihood will be more tart than you might like than with a shorter marinade. But if they were left out, yes toss them.

I'm in the better safe than sick camp, so I'd probably throw it out. Here's what the USDA says:
http://www.fsis.usda.gov/fact_sheets/chicken_from_farm_to_table/index.asp