TITLE: Are the mapping class groups of manifolds finitely presentable?
QUESTION [26 upvotes]: The mapping class group of a manifold is the group $\pi_0 Diff(M)$ of components of the diffeomorphism group. There are several variations: oriented manifolds and orientation preserving diffeomorphisms, etc. 
I am interested in finding out if we know any sorts of general properties of these groups. Are they finitely presented? finitely generated? ... ?
The mapping class groups of spheres can be identified, via a clutching construction, with the group of exotic spheres one dimension higher. Via Kervaire-Milnor, which relates these these groups to the stable homotopy groups of spheres, and the fact that the stable homotopy groups of spheres are finite, we know that these mapping class groups are finite. However this uses a lot of heavy machinery from surgery. The general case seems far from obvious (though maybe there is an obvious counter example out there?).
I would also be interested in statements about the higher homotopy groups as well.

REPLY [12 votes]: The mapping class group $\pi_0 Diff(S^1 \times D^3)$ is not finitely generated. 
The proof of this amounts to arguing that $Diff(S^1 \times D^3)$ acts transitively on the reducing discs, i.e. the properly-embedded $3$-discs in $S^1 \times D^3$ that are non-separating.  The isotopy classes of reducing discs form a group, and that is not finitely-generated.  
We show this by arguing that any component of the space of embeddings $S^1 \to S^1 \times S^3$ has a not-finitely-generated fundamental group.  This part of the argument is fairly classical: Haefliger-style double-point considerations. This step appears to have been known to Dax, as well as Arone and Szymik.  
Then we look at the fibre bundle $Diff(S^1 \times S^3) \to Emb(S^1, S^1 \times S^3)$.  The fiber over the "degree 1 component" of the embedding space is the diffeomorphisms of $S^1 \times S^3$ that fix the knot pointwise, which is closely related to $Diff(S^1 \times D^3)$.  The key argument is showing that none of our "interesting" elements of $\pi_1 Emb(S^1, S^1 \times S^3)$ are in the image of the map from $\pi_1 Diff(S^1 \times S^3)$. By an isotopy-extension argument they are turned into non-trivial isotopy classes of diffeomorphisms of $S^1 \times D^3$.