Filters for lenses that are not designed to accept filters

[MARKOE PHOTOE]

Saw this at the The Digital Picture this morning and found this interesting. Not being able to filter a 17TSE drove me to the 24TSE-ii which is the sharpest lens in my bag given the focal length.

Here is the article link:
http://www.the-digital-picture.com/News/News-Post.aspx?News=2906

I personally doubt whether you'd achieve uniform filtering due to the curvature of the lens.