I know Captain attends some games every now and then and he's been pretty vocal about the same thing. But really, you don't need to be there to spot it. It's extremely obvious on the telly too.
Now, there's no way to prove that it's not by design unless someone can drag Wenger on here and ask him about it, but you gotta wonder what's the most likely scenario: that a manager who has been working at top level for 25 years can't build a system where our rightback isn't constantly exposed to the threat of two forward-bombing players, or that Theo Walcott simply is tactically immature and does whatever makes him look good as opposed to what makes the team look good when faced with a choice?
The lad has one great trick in his book, and for all his faults we're usually a lot more dangerous when he's on the field. But let's be reasonable here.