Having played with you, really don't like you as a person, but I'll throw that aside for now, since I'm here to review the guide itself.
First of all, it would help if you had reasons building the way you do in original text, that way the more inexperienced players, who are the ones reading the guides, afterall, understand why they're doing things. For example, I think people are giving you too hard a time about philostone, perhaps justifying it in the original post might help. Personally, I use philostone on Shaco because I am not that good with him (read: can't manage health/mana well), but luckily I only play him in practice games.
In any case, it seems to me that by getting mejai's and philostone, you will be heavily delayed in killing power, and if you don't get those kills, you're done. Shaco starts to pan out late game, particularly AP Shaco, and if you have a mejai's and a philostone (both late game items) you aren't going to be getting the snowballing momentum you need to last you until late game. A friend of mine plays AP shaco and runs Sheen (for Mana/AP/Lichbane) and then Sorc Shoes/Mejai's. He's pretty good at it, and his early game killing power is, obviously, a little better than what it would be if he had philostone instead.
All of this said, I haven't actually tried the guide's build, so I'm mostly theorycrafting and speaking on behalf of my friend's experience. If it works, it works, but it seems like AP Shaco gimps himself on damage if he doesn't actually get any AP/Mpen early.
Thats like asking me to admit to trolls about my guides sucking, my guides don't suck and philosophers stone doesn't suck.
Philosophers stone Gives you the much needed HP regen throughout the game and sells late game for a lot more gold gain then dorans could ever pull off.