The view expressed by several here that skubalon, translated "dung" in Phil 3:8 is analogous to the "s word" in English is linguistically lazy. Even some simple research done with elementary Bible software disproves the idea.
First of all, the word only occurs that once in the NT, but it also occurs in the Apocrypha in Sirach 27:4, where it is used to refer to what is left after something is sifted through a sieve--obviously not dung, and obviously not a taboo word! Indeed any Greek-English dictionary or lexicon, easily accessible by any of you, will give meanings for skubalon which have nothing to do with the English "s word", such as in Anlex (accessed through Bibloi software: "anything that is to be treated as worthless and thrown out, translated according to the context dung, rubbish, garbage, offscourings." This is clearly not the same as the English "s word."
Even Thayer's (being obsolete, not used by pros, but available through the free e-Sword) says, "1) any refuse, as the excrement of animals, offscourings, rubbish, dregs 1a) of things worthless and detestable"
Secondly, there is no evidence whatsoever that the Apostle Paul used words which are called "taboo" in linguistics, naughty words, swear words. His style of Greek was educated, formal and difficult. If he never used taboo words elsewhere, why in the world would he use one when talking about the "excellency of the knowledge of Christ Jesus my Lord," which is light years away from the circumstance in which Greektim says he would use the "s word"??? Skubalon in Phil. 3:8 is very clearly not a swear word, not a taboo word. Anyone who uses Paul in this verse to excuse using English taboo words is just looking for an excuse to be vulgar.
"Slang regularly transgresses other social norms, making free use of taboo expressions. The use of words like ... 's***' in public media has become a mark of liberation or a sign of revolt, depending on one's point of view" (Sociolinguistics, by Bernard Spolsky, 1998 p. 36).
Why avoid taboo words? To me they are a sign of weakness of expression. There is always a better, more effective way to communicate than using swear words, taboo words. "Let your speech be alway with grace, seasoned with salt, that ye may know how ye ought to answer every man" (Col. 4:6).
Edited in: the normal Koine Greek word for fecal matter was kopros, not skubalon, and Paul never used this word, though it appears 11 times im the LXX. The word skubalon had a much wider meaning than "dung," but taboo words usually have a narrow range of core meaning, though contemporary usage (the range of insult intended, for example) may be wide.