The ASP.NET DataGrid Web control is notorious for its hefty view state size, but the DropDownList control can hold its own weight as well, especially when it contains a lot of items. For example, a page containing nothing but a DropDownList populated with ~100 items from a database will yield around 10 KB in view state. While 10 KB might not seem like much, remember that view state is a two-way penalty - it is sent down with the page's HTML and sent back during postback, thereby increasing both the download and postback time for the end user.
I just finished a page that, I think, will hold record as having the largest view state. Ever. Working on a site for a client and he needs a page that has over a dozen DropDownList controls, and each DropDownList has, believe it or not, upwards of 1,000 items. End view state? Over 800,000 bytes. In total, the page was over 2.5 MB in size. What does this mean for an average dialup user? Well, they'll have to wait nearly six minutes to download the page, and eight minutes to postback (two minutes to upload the 800 KB of view state, six minutes to download the 2.5 MB again).
Of course, I cut the view state down to a few KB by turning off view state for the page. It wasn't needed since I wasn't programmatically changing the state of the controls on the page, nor was I using the SelectedIndexChanged event of the DropDownList. But still, the page weighs in at 1.7 MB, which is still prohibitively large (even though all users are really on an intranet).