Ed Pegg writes "I did a survey of all available vector-based drawing programs, in anticipation of SVG in the next Firefox. I found 29 different vector drawing programs. Of these, 14 were free or open source. More than I expected. Did I miss any good ones?"
If it happens once, it's a bug. If it happens twice, it's a feature.
If it happens more than twice, it's a design philosophy.