[eridius]

I don't really have a good answer for you. Invite-based services are a good way to scale out without getting a huge spike all at once (even Gmail was introduced using invites), but I don't know how long Keybase intends to stick with the invite model or when they'll expand it.

As for services, each service that's supported presumably needs custom code, and also needs to have a publicly-auditable way to post a proof that cannot be done by anyone other than the owner of the account (e.g. for Twitter you need to actually tweet something, for GitHub you need to post a gist, etc). I don't have a LinkedIn account or use GitLab so I don't know if those services have an effective way to handle such a proof.

For reference, here's a ticket asking for LinkedIn support - https://github.com/keybase/keybase-issues/issues/1115. Here's one for GitLab - https://github.com/keybase/keybase-issues/issues/1242 - which documents some barriers there (such as no API to get GitLab snippets).