What about Ananias and Saphira?

We believe that the case of Ananias and Saphira could be understood in two ways.  The first would be as a case of church discipline under the authority of Peter.

Jesus had given Peter the authority to bind and loose (Matt 16:17-19) and this subject is more fully developed in Matt 18:15-20.  This authority can be seen when Paul turned a man over to Satan due to an adulterous relationship with his father's wife while the church did nothing. (1 Cor. 5:1-5)  In this case the man repented and was restored to fellowship (2 Cor. 2:6-8)  In the case of Ananias and Saphira, apparently Peter was indignant at their duplicity and lying to the Holy Spirit and chose to not show mercy.

 The other possibility is that they were not true believers and were simply attaching themselves to the church for whatever reason.  We can find evidence that in the early church there were unbelievers who took advantage of the meetings and dinners:

 Jude 1:12 These are spots in your feasts of charity, when they feast with you, feeding themselves without fear: clouds they are without water, carried about of winds; trees whose fruit withereth, without fruit, twice dead, plucked up by the roots;

 
1Co 11:19 For there must be also heresies among you, that they which are approved may be made manifest among you.

1Co 11:27 Wherefore whosoever shall eat this bread, and drink this cup of the Lord, unworthily, shall be guilty of the body and blood of the Lord.

1Co 11:29 For he that eateth and drinketh unworthily, eateth and drinketh damnation to himself, not discerning the Lord's body.  30 For this cause many are weak and sickly among you, and many sleep.

 
And we can see that there were others who had been in the faith and had later rejected it:

 
1Ti 1:19 Holding faith, and a good conscience; which some having put away concerning faith have made shipwreck:   20 Of whom is Hymenaeus and Alexander; whom I have delivered unto Satan, that they may learn not to blaspheme.

 Others wanted to experience the power of the Holy Spirit without being true believers (Acts 8:19-24).   And others were lovers of pleasure rather than lovers of God.  Yet they seemed to congregate with the true believers.

 2Ti 3:4 Traitors, heady, highminded, lovers of pleasures more than lovers of God;   5 Having a form of godliness, but denying the power thereof: from such turn away.   6 For of this sort are they which creep into houses, and lead captive silly women laden with sins, led away with divers lusts,   7 Ever learning, and never able to come to the knowledge of the truth.   8  Now as Jannes and Jambres withstood Moses, so do these also resist the truth: men of corrupt minds, reprobate concerning the faith.   9 But they shall proceed no further: for their folly shall be manifest unto all men, as theirs also was.

Whatever the case of Ananias and Sapphira (whether they had rejected their faith, or whether they were never true believers), we know that God's grace and forgiveness exists for those who are truly His.