Two issues I have is that
1). I bookmark so much and use tons of tags, but still feel that they are completely unorganized. Sometimes I just have to guess a what I might have tagged something if I want to find it again. This can easily be solved if I were to go through my bookmarks and reorganize them (like I know my husband has done), but I don't really have the time or patients for that, especially since I will continually be bookmarking things.
2). Other than actually making the bookmarks, I use them very rarely. I would say I have about 5 websites that I go to regularly (including Netvibes which brings everything else to me) and those 5 become shortcuts on my browsers toolbar. Everything else I bookmark and forget about for a long long time. Now this might change in the near future as I transition to my role as K12 librarian, but I for now, I bookmark and forget.
One thing that I have really enjoyed is the group dynamics of bookmarking when people are activeley bookmarking. I am part of the Technology Leadership Team at my school and we have a group diigo account. There are 3 to 4 people who regularly add things to this account and then I get a weekly email with a list of all the websites they have already read and recommend to me. I pick the once I really want to read or that pertain to me and then move on. This is great because I know I'm reading what others are reading and that what I'm reading is worth reading, because I trust those who recommend them.
For anyone interested, I tag a lot of library related and tech related things, as well as a bit on education, cooking and scrapbooking. Here is my delicious account: http://www.delicious.com/ElizabethKR