If you use Whideby bits to build web sites you will see that the name and ID attributes which are generated are depending on the site structure. Eg take a masterpage and the Input in Browser will look like
<input name="ctl00$ContentPlaceHolder1$Text1" type="text" id="ctl00_ContentPlaceHolder1_Text1" /></td>
The problem begins if you want to build user input forms with usability. Autocomplete remember all entrys on a specific ID and make a suggest. So if you have a field with name email you get your email address faster in the form.
Thats what i told in my classes the last 5 years (or more?)
Now that is not possible. It think it should be possible to set the ID programatacly no matter where the control is placed
What do you think?
If you agree, vote on this bug
http://lab.msdn.microsoft.com/ProductFeedback/viewfeedback.aspx?feedbackid=c33bff8e-4615-48c8-82ea-7a5986f2d49e