My admittedly prescriptivist opinion is this. When companies (it is always companies) choose to break basic rules of language, like adding stops to their names, I feel no obligation at all to make any effort to accommodate this. I use my own discretion to write their names in a way that seems reasonable to me.
I treat commercialese as a foreign language: I adapt it into my own language as I see fit. Does anyone feel obliged to write Peking in Chinese characters? Or to write any foreign name in exactly the same way as it is written in its language of origin? I write Germany, Netherlands, Peter the Great, Charlemagne, etc., etc., none of which are written the same way in their respective languages of origin. Nowadays some newspapers seem to change their designation of a country whenever its regime invents a new name; I consider this unnecessary and contrary to historical practice.
Just write Tomtom, Yahoo, etc, unless there is a specific reason not to, such as in a database; in a random weblog, there is no such reason, since Google's search is fuzzy enough (too fuzzy for my taste in fact—but that is another story). [Edited from here on:] If the rules for a specific publication demand that you should do otherwise, it is up to you to decide whether you can get away with disobedience. It is generally a good idea to at least stick with one spelling throughout a document or publication, whichever it is.
In some cases, you might have a unique chance to lead the development of the spelling of a particular term into a different direction: if you write for a major newspaper about a new institution—say, if the tax agency had a new collecting division called
Contr!butions :-)—, you might want to leave out any smiley faces and weird marks, to make the world a better place.