Forcing immediate registration – Requiring a new user to register is a reasonable request, but after you have got them sucked in. The sites which require registration as the first step are putting a barrier in front of adoption.

Having a Long URL – Say a site generates a URL which is 70 characters long or more. When you copy, paste and e-mail this URL, a line break becomes added. The danger is that people can not click on the link or it only links to the first part of the URL.

The unsearchable website- Some sites do not offer you a search option. If your site goes deeper than one level, it definitely needs a search box.
Windows that don’t generate URLs – Have you ever wanted to point people to a page, but the page has no URL? Perhaps the company decided that it didn’t want referrals, links and additional traffic?

Sites without Delicious, Digg and Fark bookmarks – There is simply no reason why a company would not want its fans to bookmark its pages.

Lack of feeds and e-mail lists – Be sure to make getting information about your products and services easy by providing e-mail and RSS feeds for content and PR newsletters.

Unreadable confirmation codes – I hate that! What is the point? A visual confirmation graphic system is a good thing, but sometimes they are just too difficult to read.

E-mail addresses as usernames – I’m a member of hundreds of sites. I can not remember my all of my usernames and passwords, but I can remember my e-mail address. So why not let me use that?