User blog comment:Unevent/Hybrid items!/@comment-5266525-20130519141204/@comment-4022742-20130519232246

Miss fortune, Ezreal, Skarner and Warwick would like some of that action too. The problems still remains the same;
 * You won't out-DPS a pure AD build
 * You won't out-burst a pure AP build
 * You can't build penetration for both of your damage outputs
 * You can't be resilient and have the damage too.

So, say you build hybrid items; Hextech Gunblade, Guinsoo's Rageblade & Trinity Force. What Items do you get to compliment your build?
 * Do you go full offense, grab Beserkers Greaves, Infinity Edge & Rabaddon's Deathcap?
 * Do you spike your flat penetration, grab Sorcerer's shoes, Malady & The Black Cleaver?
 * Do you spike your percentage penetration, grab Boots of Whatever, Void Staff & Last Whisper
 * Do you compliment your defense & crit by picking up Mercury's threads, Atma's impaler & Warmog's Armor?
 * Or do you go something more "on hit" and attack speed focused by grabbing Ninja Tabi, Malady & Wit's End

Whichever you choose, you will have to leave out any of the other options. With the item base for Hybrids as they are at time of writing, there just isn't a clear path. There are no hybrid penetration items, so if you want to build any, you have to dedicate 2 items slots to it. There aren't any hybrid damage items out there that topple your AD & AP like Deathcap or IE do.

And even if there were, you still can't dedicate a slot to defense leaving you vulnerable. (unless you are Jax, whose kit makes him tanky)