The problem comes when one player posts multiple things happening, then another player responds assuming that's what happened, and by the time the DM gets to post, he has to say "actually because player A did this, the npcs would have done this, and if they did and players B and C did what they posted, then Player B is currently dead."
I've had games where I went away for a day, and come back to literally a page full of posts that were all completely invalid because one character made an assumption at the beginning and everybody else continued off it.
Also, I don't use rounds outside of combat, I prefer for things to go more fluidly than "Player a takes his 6 seconds worth of action, then player b gets 6 seconds worth of action, then NPC A gets to respond for 6 seconds." because thats not how life works. You dont get to walk around talking and doing things for 6 seconds while everybody else waits patiently for their turn.
People tend to react, respond, cut you off, etc.
Now, as to the speech, it's not that big of a deal, given that people tend to talk more in PBP than normal anyways (Much like comic books), but as I said before, I'd prefer keeping paragraphs of speech to times when people are actively listening and your character wont be interupted.
And just for humours sake, on that comment that he could've said all that in one second... if he spoke anywhere NEAR that fast, nobody would be able to understand him. The average human looses comprehension of words spoken faster than ~ 300 wpm. translated into seconds, that's 5 words per second.
To give you an example, Felix's speech was 70 words (Not counting those with 1 or 2 letters). If he spoke that in SEVEN seconds, it would sound like this :
[ame=http://www.youtube.com/watch?v=c4-CRv0ih28]steve[/ame]
Worlds fastest talker speaking 10.25 words per second.
Not saying you CANT speak that fast - just that it'd be very difficult for people to understand.
I'm not going to enforce any 'word limits' because as I said before, both comics and PBP tend to be more wordy, I just don't want too much being said without giving others a chance to respond. It's about balance and fairness. Everybody gets their time to shine, just don't try for too much.