Memorize openings?!

1. e4 d6
2. d4 Nf6
3. Bd3

This is a position I have seen a lot in play on the internet. I am black playing the Pirc and instead of the common Nc3, white choses the less than best, but not bad Bd3, and black is likely out of his book.Bd3 is not a bad move, there is no "refutation", and it seems logical to protect the e-pawn without blocking c3 to support the d-pawn. 3...e5 is met by 4.c3 as is 3...Nc6.

Understanding of the general ideas of kingside fianchetto with an opposing pawn chain down the long diagonal is what you need to play black here.

Similarly quickly out of the book is a game of mine from the recent Region VI open (Sept 2010) with a strong class B player (1766) (Analysis with help of Fritz 12)

Lu,Kevin-Newshutz,Robert
 1.e4   d6
 2.d4   Nf6
 3.f3
I think this is a way to quickstart the normal anti-fianchetto kingside attack, so I abandoned the fianchetto and went into an "open game" where I hoped f3 would be misplaced.
 3...   Nc6
 4.c4   e5
 5.d5   Nd4
 6.Nc3  Be7
 7.Ne2  c5
 8.b4   O-O
 9.bxc5 dxc5
10.Rb1  Rb8
11.Nxd4 cxd4
12.Na4  Bd7
13.Nb2  

This does not look much like a Pirc! I misunderstood this position and played:
13...b5??
I need to ensure control of d6 and c5 and keep his c-pawn backward or try the sacrifice Nxe4!? to get a dominant central pawn mass and open lines toward his king after 14. fxe4 Bb4+ 15. Kf2 f5 16. Nd3 fxe4+ 17. Kg1 Bd6 18. c5 exd3 19. cxd6 e4 black has more than enough compensation for the knight. Nxe4 sacrifices are thematic against a f3,e4,d5 pawn chain and an un-castled king.
14.Bd2  Qb6
15.Nd3  Qc7??
16.c5   Rfc8
17.c6   Be8
with a significant advantage to white.