Would say it comes down to what risk you are willing to take.
If you use a logo without permission especially from a larger corp, you might run into legal issues or maybe even jeopardize a deal that is in the making with your company.
Some public record clearly stating that a company X is using you can help to migitate the risk (public Job posting, article, webinar, etc.)
And of course always take down the logo if someone from the company is complaining. The very best is always to get permission from the companies marketing, business, legal or sometimes even hiring department, depending on the market you are in. Would recommend to go for case studies highlighting them and their solution and then get the logo that way.
If you use a logo without permission especially from a larger corp, you might run into legal issues or maybe even jeopardize a deal that is in the making with your company.
Some public record clearly stating that a company X is using you can help to migitate the risk (public Job posting, article, webinar, etc.)
And of course always take down the logo if someone from the company is complaining. The very best is always to get permission from the companies marketing, business, legal or sometimes even hiring department, depending on the market you are in. Would recommend to go for case studies highlighting them and their solution and then get the logo that way.
Hope I could help a bit...