You can take up to 1200mg of ibuprofen at a time (per a sports doctor I know) and I've done it. Sometimes the pain calls for it. Frequency of ingestion is really the worst thing - it'll grind a hole in your gut if its frequent enough.
Too much ibuprofen can have an affect on the liver, though not nearly as bad as acetaminophen (Tylenol).
Recent studies have shown Aspirin to have many benefits: anti-cancer, cardio-protective etc. I don't feel like it works as well as ibuprofen for joint pain though.