There's two ways to look at this. One is that by linking out you're telling Google what your site is about and placing yourself in the neighbourhood of those great sites you link to.

Two, is that you're leaking.

The second, leaking, has numerous threads here indicating recently that stopping the leak helps their rankings. The first way, I've never seen anyone say that it's directly impacted their rankings.

So, I don't like it, but the emperical evidence seems to say that you should stop the leak.

I'm of the experience that adding nofollow tags to a few sites I recently revamped helped serps.

I can't conclusively suggest that it was indeed the nofollow tags that were responsible--it could have very well been a number of other factors including cleaned up html source and the like. However, the nofollow tags were the only new item I added and hence the cause and effect in my mind.

Just my two cents.

> Am I leaking "Link Juice"?

Depends.
If you have 1,000 inbound vs. 6,000 outbound links = you're probably leaking.
If it's 10,000 inbound vs. 6,000 outbound = it's the natural "web".

Open directory. Lot's of outbound links. No leakage.

Exceptions:
When inbound/outbound quality are not balanced. Junk vs. Authority

Open directory. Lot's of outbound links. No leakage.

And doesn't rank.

Wikipedia. No outbound links. Ranks like crazy even on competitive terms.

How would the open directory rank if they nofollowed all the links? Probably like Wikipedia does. they'd have no editors, but they'd rank :).

Don't wanna open can of worms about open directory ranking. It was used for PR example.

The nofollow tags is not necessarily what makes Wikipedia rank well.

>>>And doesn't rank.
The reason it doesn't rank may be from other reasons, particularly from a preference for showing sites with the actual answer to a query as opposed to a site that has links to other sites that may have the answer.

>>>Wikipedia. No outbound links. Ranks like crazy even on competitive terms.

Wikipedia ranked well before they nofollowed the links.

Depends.
If you have 1,000 inbound vs. 6,000 outbound links = you're probably leaking.
If it's 10,000 inbound vs. 6,000 outbound = it's the natural "web".

So we've about 20-30,000 inbound links. Does that mean I shouldn't put the nofollow tag on my outbound links and keep my site looking "natural"?

Maybe the first place to start is, how are you currently ranking?

My first thought from the original post is nothing to do with "link juice". If you didn't realise how many links you had it suggests that you haven't been checking that they are still valid.

Outbounds that are broken or go to parked pages do nothing for your site's credibility with your visitors. I would at least scan for broken links before doing anything else. I don't know of any way to automate checks for parked pages or moribund, out of date, sites however.