If you are conducting link audit, you have to keep track on bad links that are coming from gambling or adult sites. Search engines always keep an eye on bad links a website has. The higher the percentage of links from such sites, the more badly it is seen on the website. Trust is very important to build between search engines and a website. The bad links can have adverse effect on the trust factor of the website.
By analyzing the website of a competitor, you can determine if there is any good place you have to focus your activities. This way, you can also find out what type of competition going on. Suppose if one competitor has 10000 links and another has 15000 one-way links, then your website with just 5000 links has a lot to do to stand out before it can compete in same space. When it comes to develop strategy of link building, you have to create schedule for diverse activities.