If you need (or want!) more space than Dropbox gives you, consider
copy.com (my referral link, gets us both an extra 5GB if you sign up) instead. 15GB free for each person, 5GB for each referral (both you and the person you refer get 5GB each), and none of these silly referral limits. I have 105GB through them free for life right now
Not sure what Dropbox's limit is, but I have right now 10GB with Dropbox and only half of that is free for life. The rest is from limited promotions and things that should start expiring in the next year or so.