Lots of characters, but no Character Development
Looking over the anime series that I've really liked, a promenant feature of them is that they have a very small group of main characters (like 3-5). Most series aren't like this though and tend to have about 12 main characters. I feel there's a really noticable difference in quality as a result of this difference. I can't think of one above average series that has a huge group of main characters.
The problem with it is that because of the number of characters the amount of time for character development is really restrained. When it does happen it comes across as really superficial and forced.
For example, I recently watched Macross Frontier and felt it was really let down by the excessive number of focused on characters. I remember the original Macross series didn't suffer from this at all and it was very focused on the 3 main characters even though there were many other characters.
I don't watch as many series as a lot of other people, so how much of a problem is this?