There is no publicly posted limit, that I am aware of.
That said, even having 1,000+ contacts can and does create a huge amount of traffic, if not just because of constant status changes for all contacts.
Is there any reason, why you would need to do this?
IMHO, it's not a very good design.
It would be much easier to simply have open privacy for a skype name, and even simply pre-authorize other Skype names, if needed vs. formally adding every Skype name to the contact list.
Many programmers, do not understand that there really are ("two") possible authorization methods:
1. To authorize communications with another Skype name. Not formally, adding that Skype name as a contact, but authorizing that Skype name to be able to communicate with your Skype name. Because no formal ("Add Contact") request is needed for this. Note: You cannnot see what the online status is of the Skype name, in question, that you authorized. When using this method. But, they are allowed to contact you, even when you are not using Open Privacy.
2. Formally, sending a ("Add Contact") request, which does allow you to see the online status of the Skype name, in question, once that Skype name approves your request.
Note: Using method 1, does not allow you to contact the Skype name you approved, unless they have:
1. The Skype name in question, has Open Privacy.
2. The Skype name in question has sent you an ("Add Contact") request, which will then be automatically-approved, without any manual intervention, since you already have authorized them.
While this shows the use of method #1, it is for the Skype Desktop API and not SkypeKit:
http://devforum.skype.com/t5/Desktop-API/Is-this-a-bug-or-by-design/m-p/13859#M667
