Kristine and Luis are vastly different in the way they respond. Luis, as I recently told them, has all the charm of a brick in the face.

One gridseed will reach the cap, or close enough to CPU mine the rest of the way. Any more is just giving them free hashpower to steal.

Multiple accounts on the same IP will get both the IP and all the accounts blocked, so you earn almost nothing. This applies even if they belong to different people! Such as when you refer family members or a visitor is mining on their laptop. They seem totally disinterested in removing the blocks.

Referrals on the same IP, for example if you show someone the site, and they accept your referral, will not show up. They won't change referees, and you can't reuse emails, so it would take a new email, on a different IP, to fix this.

Yes, it is almost certainly a scam. Exactly what is still not clear, but they are definitely stealing and reselling forfeited hashpower as contracts. And the likelihood is they will eventually disappear once they have enough long-term funds on hand. Don't be tempted by the promised returns.

To verify once you reach the 10 euro limit, either use a disposable Visa/MC, or buy a DEMO contract with BTC. Do not give them access to any more money than absolutely necessary.