This virtual card is promoted by banks here in Portugal, and the entity that issues them is the national credit card regulator. There is no doubt about their credibility.
They are highly used here because most people are afraid of using their real cards, afraid of fraudsters and unsafe sites.
But as you said, DreamHost may not accept them because you have to fax a copy of a real card to them. So they may not be an option here.
Apart from that, I have a real credit card for many years, but I only use it in 3 or 4 places: Paypal, Amazon, Clickbank and Google. For all others I use a virtual visa. I don't trust my card to any employees from a company I don't fully know.
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