Textanz is text analysis tool, counting frequencies of repeatable words and phrases in document. Such information is very useful at least in following situations :

(1) checking your document for unnecessary repetitions and words-parasites. Extremely important in business documentation, where reader's impression influences directly to your bank account ! And, good idea for personal informal correspondence as well.
(2) analyzing someone's text : find out his/her favorite words and constructions, evaluate writing style, know more about the personality of authors. Must-have for psychologists and literature critics .
(3) finding cross-quoting in two texts : having them one after another as single text in Textanz.
(4) programmers : search for repeatable code fragments . Textanz will find them dependless on spaces, tabs, linefeeds, etc.
(5) web-masters : calculate word density in html page and choose keywords for META-tags.
(6) words frequencies is important factor in linguistics research . Textanz is able to search for word parts of specified length, so it is possible to count words in all their forms.

Absolutely no risk : Textanz does not change the original text, only scanning and analysis.