@Buscemi: I see, so you're one of those guys who uses annoying skillshot APs. Anyways, like I said, it's situational. In cases where there are no skillshots to dodge, starting with a Doran's Ring is pretty safe, but otherwise boots are a good bet.
Anways, on the issue of Bloodrazor, that item is literally only viable on like 3 champs, and only one of them is ranged AD (Kog'Maw). Madred's Razors build into Wriggle's, though, and help with buff/dragon securing due to the proc, besides the fact that they give perfect stats for AD carry vs. AD carry (armor and AD). If you duo queue with a lane mate all the time, you're probably used to going against two solo queue guys, but I'll tell you that a decent carry/support combo will make you wish you had cloth/5, especially if you're facing, say, Caitlyn. There are a lot of bad players and a lot of players who don't work together well (which is why I avoid bot lane like the plague in solo queue), but two good laners who are on the same page will just have too much of an advantage starting with either Dblade or cloth/5 (depending on who they are and whether they need the cloth).
Wriggle's is one of the most cost-effective items in the game for what you get out of it, and you can't beat the stats for the price. Past early laning when you're lasthitting it also becomes quite useful for pushing lanes (because of the proc). It's a safe buy for any AD champ pretty much universally. And the best way to think about it is this: a BF sword costs 1650, but just gives 45 AD. Wriggles has a good active, a good passive, 23 AD, and 30 armor for 1600. And even though it doesn't build into anything, it's certainly cost-effective to use it while you fill out the rest of your build, and then just sell Wriggle's for whatever final item you're going to buy.
Also, Black Cleaver...isn't the best item to use. Especially with the new masteries (which has a 10% arpen one), Last Whisper is the better item to take on a carry. To look at the math, the flat arpen of TBC reduces armor by 45 at 100 and 45 at 200, but LW reduces it by a percentage, so while at 100 armor LW gives 40 armor reduction, at 200 armor that reduction is 80, making it both more universally applicable and more effective at killing high-resistance targets. Granted TBC increases the damage of your whole team, but being the carry, you're the primary source of physical damage, so your damage is most important. Also, LW increases the effectiveness of your abilities against armor, so it makes, for instance, MF's ult hit harder against targets with resistance. SInce TBC's effect only procs on auto-attacks, it's less reliable when talking about increasing ability damage.
Buying both is also inefficient, because TBC lowers the armor of the opponent, meaning it lowers the value that LW takes for the % armor reduction, which is inefficient. Much better to get, say, a Bloodthirster (or two).
We play as a team of five. We know each other and have played for a year or so. I'm not really the main AD carry, as I'm more of a solo top or mid kind of guy. To the matter at hand. Over a hundred armor LW is more viable, that's true. Now, I wouldn't bet that too many players go for that, but it's an option. I like to go the Phantom Dancer+Infinity Edge way, with a Black Cleaver, or if they're stacked on armor, a Last Whisper. And let's just be clear about one thing, MF's ultimate is only ever viable in a team battle if you have great positioning and another ultimate that can stun your enemies, say Sona's. Otherwise it's all just a waste of time, or a lane-clearing ability.
I don't like to go Wriggle's because I hardly ever need to. My support will heal me as Sona or Soraka, and shield me as Janna. I don't need the ward it gives, the support takes care of that as well. With two Doran's Blades and a Vampiric Scepter I have the same sustain to stay in lane as a Wriggle's. I get the same amount of attack damage, but I don't get the armor. What I do get is HP. It basically comes down to taste. Both ways will have you selling them sooner or later, with similar stats.
One of the many things that fascinates me about League of Legends is the starting item choices and how it varies in different parts of the world. Doran's is an American style of playing where as boots or other ingredient item + pots is more European.