Is This Conisdered Over-Optimization (Internal Linkng)?

5 categories each with 20-50 posts belonging to them. Each post in the category lists all the other posts in the same category in the sidebar.

For example, if a category has 30 posts belonging to it then you have this structure x30:

Category

TVs

Post Title

TV 1 Review

Sidebar

TV 2
TV 3
TV 4
TV 5
TV 6
TV 7
TV 8
TV 9
TV 10
TV 11
TV 12

etc.

I removed the word "Review" from each entry in the sidebar because I though that might be troublesome. However, all the permalinks obviously still have the word "Review" in them.

I also link to all products on each category page, as well as each relevant product on the product's brand page.

As you can see, this leads to a hell of a lot of links pointing to the same pages with exact anchor text (minus the word review).

Thoughts?

you also added tv 10 times to each page. I would suggest showing only 3-4 related posts . there is a plugin that shows random posts from same category in sidebar , try that out .

Are the TV's product numbers or do they actually have the word TV in it? If so, you are probably overoptimized for TV, unless you have really long articles. If it is like this in the sidebar:

Sony KDL456
LG BLAHDIBLAH
JVC TEETY
Sony TLF

You should be fine. Just watch the amount of times you repeat the brand name, and make the articles longer to dilute them if you feel % is going to high on certain terms.
Use http://tools.seobook.com/general/keyword-density/ to track this.

I tend to aim for below 1.4% just to be safe.
(This is just on page, be careful with external anchor texts targeting phrases too.)

Thanks for the advice. I don't think external linking will be an issue, as I tend to use naked urls and branded links more than exact match.

TVs isn't actually the niche, but the same principle applies.

It's a bit mixed actually:

Sony KDL456
LG BLAHDIBLAH
JVC TEETY TV
Sony TLF TV

I think I'm going to limit the number of sidebar links by nesting deeper - create a category for each brand and add each product to that. Should just keep it down to a max of 5.

I don't know whether this new sandbox exists or not, but the only thing I've changed for this site is the internal linking structure and I'm literally getting no visitors at the moment, which really is terrible with the number of posts I have.

Check out PHPBuilt's authority site building thread. He addresses this issue. I don't use categories so I can't understand your organization here, but odds are you are over optimized just by having that many categories with keywords in the permalinks.

just remove sidebar and link to similar articles manually .
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Reduce the number of posts shown on the sidebar to 10 and use a 'related posts' plugin to show related posts at the end of each post. You can also edit your theme so it stops showing permalinks. That can help decrease the number of exact keyword occurencies.