Should I use Limit contacts per company?

When enabled, this feature would allow you to set a maximum limit on the total number of contacts at each company that you're willing to use ad spend on.

When it might be useful:

For example, your audience may target the Technology sector and include large enterprises like IBM however, you do not want to spend your entire ad budget engaging IBM employees. 

In this case, setting the Limit contacts per company to 30 would allow you to control how many contacts at IBM (and other large enterprises) see your ad which helps avoid blowing your budget on accounts that aren't ready to do business with you yet.

Drawbacks:

The contacts that are included are selected arbitrarily and aren't necessarily sorted by attributes that would make them more valuable to you (eg, seniority).

Additionally, by setting a limit on the maximum contacts per company, you are only targeting accounts that have at least the value you set for the limit. For example, if you set the limit to 30 then, only accounts with at least 30 contacts will be included in your targeting.