how much space do you get with dropbox free
This is pure speculation, but: Dropbox had 1 M users in 04/09, 3 M in 11/09, and 4 M in 01/10. If the growth has continued in a linear manner, they should be around 8 M now. Let's assume that they are between 6 M and 10 M users. The free account gives up to 2 GB of storage space. I would guess that the average usage rate is less than 50 %, i.e. less than 1 GB per user. Let's assume the average storage per user is 500 MB to 1 GB.