Typos and variations

Search engine analysis must identify the common typos and various ways to write the search term.
Lets look at the following examples (all numbers are according to overture, June 21 2007):
- Search engine optimization - 117,593 searches per month
- Search engine optimization seo - 5,071 searches per month
- Search engine optimisation - 5,854 searches per month

- Ekg - 13,773 searches per month
- Ecg - 11,503 searches per month

The first example tells us that going after the typo (search engine optimisation) will get you more traffic then the obvious choice (search engine optimization seo).
The second example tells us that a heart/ medical web site must catch both terms (ekg and ecg) since they are almost the same