Once only used to end sentences, emo-pop culture and teenage angst are making the period the new cool way to emphasize (usually moody-ass) sarcasm, strictly through textual means.
Note: This does not apply to the practical and traditional use of the period, especially when capitalization and other punctuation exist within the text. That is grammatical correctiveness, and not just some damn way to express a total and annoying state of nonchalant moodiness.
See a Zumiez gift card or T shirt or sarcastic, delved-in-internet-culture friend for reference.
Person A: hey John, how have you been man?
Person B: im ok. i guess.
Person A: you sure? you don't sound so well..
Person B: are u done talking yet. kthx.
thx zumiez. way to fcking further teenage angst bullshit.