That or fickle fans.

I personally think it has been a mix of both. Few footballers are completely consistent... Theo may be one of those who has longer hot and cold periods... Even mighty Gerrard has them...
but if the lad goes to a World Cup way before his time and isn't played... it's not his fault. If he scores a hattrick in one England match- and then doesn't the next- doesn't mean he needs his nuts ripped off and shoved down his throat.
I think the media has been very unfair to Walcott- praising him more than they should at the slightest promise- and then shredding him at the slightest disappointment. He's not as good as Messi- and shouldn't be expected to be... at the same time though he is a player that seems to give a lot- be very athletic- and prone to moments of brilliance. Even when he's not got scoring boots on- he worries defenders due to his pace- he is someone that needs to be watched.
Fully admit though- he has cold periods.