With Steemit being the public face of steem right now, it seems to me that a comparison with Reddit is appropriate. Comparison uses Reddit statistics from 2015

|          |Reddit | STEEM | Approximate Ratio|
|----------|:-----:|:-----:|:----------------:|
|Total Users    |234M|25k|10,000 to 1|
|Votes/day    |25M|50k|500 to 1|
|Comments/day |2M|6k|300 to 1|
|Posts/day   |210k|4k|50 to 1|

Reddit has a market value of approximately 4 billion dollars, so the current value of Steemit should be between $400k and $80M depending on which metric you look at, with Steemit doing surprisingly well on the posts per day front. What we see here is a small, but passionate community with high productivity on the post side. Web valuations have traditionaly been based on eyeballs so my guess is that the present value is closer to $400k than $80M

With over 100M STEEM in circulation, I estimate the value per STEEM is between $0.004 and $0.80.

That's a lot of uncertainty, and doesn't take into account the possible upside, or possible downside. Reddit is also a very different sort of beast, but this is just about the relative worth of the value provided today by Steemit and Reddit.

Sources:
http://www.breitbart.com/big-journalism/2015/07/16/ellen-paos-ouster-preserved-reddits-4-billion-valuation/
http://expandedramblings.com/index.php/reddit-stats/
https://coinmarketcap.com/currencies/steem/
https://steemd.com/distribution
https://steemle.com/charts.php