what is the disadvantage to milling grain too fine?

I have just ground a batcch of malt and it is a little finer than i usually grind aand was wondering what effect this will have on my beer? The hull of the malt are all in large peices and not shredded so hopefully tannins shouldn't be an issue so what other effect will this have on my beer?

define "too fine"? Powdery? Or just small grits?

It sounds like you got a very nice crush if the husks are mostly popped open and relatively intact. I wouldn't worry, at all.

I mill rather fine and for low gravity beers, it can mean getting all the sugar out before having a full kettle. Recently, in setting up a commercial mill, we had a bad cam that was making too much dust. It resulted in a gummy mash and very, very slow runoff.

Mainly small grits although some powder so sounds like it should be ok then. Excellent.. Thanks for your advice.

It wouldn't be a bad idea to buy some rice hulls. Just in case.