Hi,
Good question. It is highly important!
Although, there are various considerations to determine what to keep and what to disavow.
Inbound links are like letters of recommendations in the real world.
Therefore, it is perfectly natural and very important, to have recommendations from other operators in your industry/niche, universities, linkedIn accounts, as some examples.
Other natural good websites might be, serious aggregators/directories, serious websites for announce your events, high quality press, as some examples.
A second and equally important factor, is the spam score of the website. You can check with the Moz Site Explorer or the MozBar. Also highly important factors are the page authority "PA" and the domain authority "DA".
If you consider that is not relevant for your website and having high spam score, I recommend to disavow, both in Google and Bing.
Of course, it is a task that should be done carefully, studying each link, one by one and following the Webmasters recommendations from each search engine due to they are not equal.
Here is a complete guide by Marie Haynes.
Ma Verónica B.