I thought you'd appreciate this correspondence between Jeff Smelser (a Northern Virginia Centerville preacher) and Edward Hobbs, N.T. Greek professor. It's great primary source material on the subject. I received this as part of the Biblical Greek (bgreek) group at ibiblio.-- Ed Anton
http://www.ibiblio.org/bgreek/test-archives/html4/2000-03/36019.html For more on the proper translation of eis, click here.
Finally, if eis means "because of" in Acts 2:38, what about Matthew 26:28? Was Jesus' blood poured out because we were already forgiven? Of course not. All standard translations of Acts 2 are correct. This common preposition occurs nearly 1500 times in the NT. Not once it is translated "because of"!