Comment by phyzome
The DNA itself is not "anonymous", but I would do it without giving my real name, address, etc. They could know who the DNA is related to, but not gain more information than that.
Even better would be to swap identity with someone else who wants to get sequenced...
They would be able to pinpoint your identity (e.g. "this person is the son of both X and Y, and we know who X and Y are").