Another negative side-effect would be that each link would be worth less SEO-wise. You see, the more links coming out of a page, the less these links are worth. Let's say you want to do inlinking (linking to other pages of your own website) so some authority coming from your main page can be passed on to the other specific pages, this won't be worth as much if you have thousands of other links coming out from that page.
This can easily be resolved by checking/ ticking off unnecessary or duplicate labels.Remember to use labels wisely and not just put any topic that comes to mind.
2. Lay off putting too much ads. It won't be effective as you will be overpowering your content and no one would want to go there anymore, let alone click on your ads. Too much would also not look very nice for the aesthetics of your website.
You will also look shady to the the typical passerby who might come by your site. No one likes a site where they feel that you are just there to sell them something. First and foremost you have to capture them with good content, and from then there will have a higher chance of them coming back to eventually click your ads even if there is just a few.
3. Lay off using too many widgets. Only use those that are most useful and important. Having a lot will effectively slow down your page, and we know for a fact that page load speed is factored into Page Rank.
4. Lay off putting too many posts in a page. The number of posts that you should have in a page will highly depend on what kind of site or blog you have. But 7-12 can be a good number so that you won't effectively slow down your reader's PC too much whenever they load a page. The longer it takes for them to open your site, the higher the chances that they will just leave without even seeing what you have to offer. On the other hand, if they are a regular reader, chances are they won't be reading all of your posts anyhow.
5. Lay off blinking ads. To be honest they ARE eye catching, and they hurt my eyes. Take them out, they can be really annoying to the regular reader.
6. Lay off the reciprocal links. They don't work anyhow (SEO-wise) and they will just clutter your site. To top it off, you might even be penalized by Google.
Maybe what you can do is make a page dedicated to the blogs or sites that you like and want to link to. But don't make it such a way that you will simply link to anyone who would link back to you!
7. Lay off too much text / Lay off too much images
Again, this will highly depend on the content of your site, but a balance is always good.
If you can, try to place an image on every blog post. This is a good way to capture your reader's attention especially if your blog is too 'wordy'. On the other hand, too many images can easily slow down a page, so make sure you don't put too much. It may catch your reader's attention, but they may grow impatient with the slow loading time.
8. Lay off too many colors. Sometimes this just makes things confusing and hard to read. It can also give one a headache if there are too many contrasting colors on your site. Having only a limited color palette can even make your site have a more professional feel.