Do backlink tools ever show more backlinks then there actually is?

[john]

I was wondering, because I see the numbers very unlikely for some websites.

[Richard]

There is no such thing as a perfect tool. Most likely, they will show lesser number than the actual. But for instance you are running a campaign focused on Google, then make sure to check the analytics or webmaster tools. Same is true with yahoo/bing where you should claim your bing websmaster tools. Third party tools such as alexa, backlinkwatch, traffic travis, seo spyglass gathers data from all types of places. So as you can see, a certain tool might only cover a certain scope so you will need to combined functionality from several options.