Storing JSON inside a text or blob column

[Joshua Nisenson]

I am creating a database design for a web site that will present users with a dynamic and vote based grid. Inside this grid they will be able to vote on many topics and these topics will change daily, weekly or monthly. The users will be members of 1 to n different groups and the measures/topics for the groups will be the same but the votes could be different based on the group type.

If I have 1000s of users, 100s of groups and 100s of topics, the storage needs could get pretty large, specially if the vote history is stored over time. So my question for database design is as follows:

Would it be good practice or design to store JSON encoded strings inside a specific text or blob column to save space? How is this usually done?

For example:
If I had member A, who was a member of 3 private groups.
The 10 Vote measures were presented to all 3 groups but the member wanted to vote a couple different ways based on the group type.
I would end up with at least 30 different votes for that member that would need to be saved. If I could store all of the choices within a JSON string it would save a lot of space.