My theory, which was thought up of by a friend.
Ok well we know the doctor has been deleting himself from all databases so be isn't so big, and as someone else said, everyone is asking Dr Who?
The theory is that somehow the doctor will also forget who he is and Clara has been scattered through time by someone, possibly himself, to remind him who he is. The evidence for Clara's involvement in this theory is that both time she has died what does she say? "Remember". *dadadaaaaa*
Also, another theory I saw on tumblr somewhere is that the TARDIS is trapped in different timestreams; the whole reason this theory came about can be found by going onto ABC shop and searching + reading description of the Temporal Sonic Screwdriver- accidental spoiler by ABC somehow?