No, whether you want commas depends on the sentence. Most good writers wouldn't punctuate that sentence as you did. Too halting for such a short sentence.
But this is not the point here, is it? The point is that any abbreviation with periods in it could appear in the middle of a sentence.
i can only think of three exceptions where you'd need capitalization for additional information: acronyms, proper names, and abbreviations.
i've been doing this as a test since may 13, 2009. i've never run into the problem of a misunderstanding before due to lowercase and i usually write this way in all casual written forms of communication (email, sms texting, blogs, comments). i originally picked it up from a designer i admired back in 2008, and the habit kind of stuck after trying it.
But it's not about misunderstanding. We've all been on the Internet long enough to be able to slog through 1337speak and poor spelling and grammar, if we have to, with probably 99% understanding. However, it takes longer. As it is with capitalization--it doesn't prevent overall understanding, but it does slow it down, at least a little.
That said, maybe that's acceptable to you. Maybe you're going for a certain aesthetic.
the point pg made, which i was responding to, was: "it's not about being improper, it's that you're giving the reader less information," so i was addressing that.
the original point was "does it slow you down to read this blog because there are no caps?" i don't know whether a majority of people read lowercase slower--nobody has mentioned it since i started doing it a year ago. i personally have no problems with it; i'm not doing stuff like omitting vowels (an extreme example to make a point, imo). i'm just skipping over the shift key.
it's not about aesthetics in my case. more about laziness in typing, and i don't want to do something just because "that's the way it's always been done."
only 1/3 of the periods in, e.g., this sentence, signal the end of it.