hmmm, my whole attitude to uploading my work on to the web SINCE day one has been this: If its something I'm very serious about or really don't want stolen (something you've put a lot of time into and is your original idea) then I wont upload it period. Instead I usually wont even scan it. Here is a fact. THe internet is a nasty place with nasty people - it's not a secure place plain and simple. Anyone and their 2 year old cousin can press printscreen and save whatever is on their screen - anyone can steal anything. Sounds harsh but it's reality. I do post stuff on DA that:

a) wont kill me if someone happens to take it and do whatever with it (sketches, works in progress that im not completely serious about)

b) Animations (not exactly something you can plagerize - and get money for - especially if its school assignments)

c) Basically NOT something I would make money off of in the first place ( that pretty much sums it up)

For the most part I'd be pretty much against posting character designs or layouts for animation that you would put in a portfolio - simply because they can be copied and they can be stolen - very easily.

Anyway thats my $0.02