In the first season, Ianto struck me very much as throwaway character, something created just in case they needed extra cannon fodder around the hub. The writers were originally planning to kill him off, and really, it showed.

Actually, you kind of see this pattern with all the Torchwood characters. It's somewhat amusing and a little sad that in a show that's run two seasons, they still don't know what exactly they're trying to do with it. (Or, here's to hoping the 3rd season is the one where they get their act together.)