A bit harsh TimS! Granted 4...d5 isn't going to suit your bloodthirsty Sicilian fan, but it does suit some players! I'd especially recommend 4...d5 to those who want to fight in a complex queenless middlegame which White may well not know too well. Thus 4...d5 might work for such a player against a lower-rated but booked up white opponent or to hold a stronger opponent - remember Sokolov-Zozulia?
Personally I've done OK with 4...d5 at blitz, and I seem to recall Jonathan Rowson quite liking the idea, but, granted, it won't suit everyone!

I recall someone playing this against me at the local chess club.  In the first game I tried the Smith-Morra using the move order 1 e4 c5 2 d4 cxd4 3 Nf3 Nc6 4 c3, when he played 4...d5 (presumably he'd learnt the Capablanca defence to the Danish/Goring and played by analogy, though I don't think it fully equalises against the Morra).

The next game I varied with 4 Nxd4, and, not realising that I'd transposed to the Open Sicilian, he still continued 4...d5.  I can't remember what I responded, but I recall I had no problem proving an advantage.  Looking at the position fresh, 5 exd5 Qxd5 6 Be3 with Nc3 to follow looks good, or 5 Nxc6 bxc6 6 exd5 Qxd5 7 Qxd5 cxd5 8 Nc3 and Black's queenside is decidedly loose.

I'm not averse to playing dubious lines with Black if they offer good practical chances and traps, but this line doesn't even offer any of those, as far as I can see it's just inferior.

I have the Dangerous Weapons book as well, which says that White is slightly better in a number of variations, although if Black plays precisely he can gradually equalise. 

I can't really find the practicality in this variation, since against weaker players there are not enough winning chances, partly because Black's position starts out as being slightly worse, and against stronger players, the adoption of this surprise weapon would probably result in you getting outplayed or ground down by the opponent.

Good morning/afternoon,

What is your opinion of the 2.Nf3 Nc6 3.d4 cd4 4.Nd4 d5 variation covered in Dangerous Weapons? I tried the line in a few blitz games, but simply ended up in a somewhat passive position without a lot of active prospects.