Does Luke 6:30 imply that the person asking has a genuine need? There was another thread in Mi Yodeya where a Jewish individual played a "prank" on a Christian in order to get his money ($20) since he figured the Christian was obligated to give it to him if he asked, according to his understanding of Luke 6:30. Needless to say, this Jewish individual, since he admitted it was a "prank," didn't have a genuine need for the money.

I have been approached many times by people who were scamming for money. 

For example, I am approached by a man/ woman outside a grocery store, as many people are. He/ she says, "My truck broke down and I need to call a taxi." I tell him/ her I don't have any money on me, which is the truth. I rarely ever do. I go into the store, and as I walk out, I witness the same  individual driving down the street in his/ her car. It was a scam. What were they scamming for? Likely narcotics or alcohol.

If I had given this individual money, they would have likely used it to buy narcotics or alcohol. Essentially, I would be contributing to and enabling their lifestyle --- a lifestlye which is by no means beneficial for them. In fact, if they bought narcotics with my money, they could very well overdose and die. 

A culture of drug abuse didn't exist in the time of Jesus. But, it does today.

Hence, my question. Should a Christian indiscriminately give or lend his money (if indeed he has the money on his person) to everyone who asks him? Should a Christian discriminate who and who he does not give his money to?

If so, what are some things that could assist a Christian in this situation?
I don't see that there's a definitive answer to this.  There doesn't seem to be a whole lot of consensus on this one.  Even the major commentaries, which usually find some common ground, disagree.

A few examples:


  Clarke's Commentary on the Bible  (This agrees with the teachings I've heard on this verse.)
  
  Ask them not again - Or, Do not beg them off. This probably refers to
  the way in which the tax-gatherers and Roman soldiers used to spoil
  the people. "When such harpies as these come upon your goods, suffer
  the injury quietly, leaving yourselves in the hand of God, rather than
  attempt even to beg off what belongs to you, lest on their part they
  be provoked to seize or spoil more, and lest you be irritated to sue
  them at law, which is totally opposite to the spirit and letter of the
  Gospel; or to speak bad words, or indulge wrong tempers, which would
  wound the spirit of love and mercy." Of such as these, and of all
  merciless creditors, who even sell the tools and bed of a poor man, it
  may be very truly said: -
  
  Wesley's Notes
  
  6:30 Give to every one - Friend or enemy, what thou canst spare, and
  he really wants: and of him that taketh away thy goods - By borrowing,
  if he be insolvent, ask them not again. Mt 5:42.


So, having said that there may not be a definitive answer, in context, the principle seems to be that we should assume the asker has a real need.  This has the obvious implications of leaving us open to fraud, scam artists, and the like.  Christ seems to be, in this case, telling us to put the principles of love and faith first, showing the love of God, giving sacrificially, trusting that the asker has a true need, even if we can't know for sure.  In other words, it's better to give willingly and be taken by a con artist than to try to be shrewd and not give at all.  And if we get taken, not to be bitter about it.

This is hard to take for a lot of us. (Me included.)  It's very easy to be bitter about being taken advantage of, and it's very easy to have the mindset that we're not doing thieves a favor by letting them profit by taking advantage of trusting individuals.

However, this verse is smack dab in the middle of a slew of verses that teach the same basic principle:  Show meekness, mercy, and kindness to those that do not deserve it.  In my Bible, this section is under the heading "Love thy enemies":


  Love for Enemies (NIV) Like 6:27-36
  
  27 “But to you who are listening I say: Love your enemies, do good to
  those who hate you, 28 bless those who curse you, pray for those who
  mistreat you. 29 If someone slaps you on one cheek, turn to them the
  other also. If someone takes your coat, do not withhold your shirt
  from them. 30 Give to everyone who asks you, and if anyone takes what
  belongs to you, do not demand it back. 31 Do to others as you would
  have them do to you.
  
  32 “If you love those who love you, what credit is that to you? Even
  sinners love those who love them. 33 And if you do good to those who
  are good to you, what credit is that to you? Even sinners do that. 34
  And if you lend to those from whom you expect repayment, what credit
  is that to you? Even sinners lend to sinners, expecting to be repaid
  in full. 35 But love your enemies, do good to them, and lend to them
  without expecting to get anything back. Then your reward will be
  great, and you will be children of the Most High, because he is kind
  to the ungrateful and wicked. 36 Be merciful, just as your Father is
  merciful.


This tells me that this passage, taken in context, tells us to trust, even when it may be foolish to do so.  After all, the things of this world are temporary.  

In short, there may be no definitive answer, but taken in context with the surrounding verses, the answer seems to imply that we are to assume there is a genuine need, even if we are skeptical.  It doesn't imply that a genuine need must exists.  It implies that we are to assume that such a need is genuine.  We are to trust, rather than doubt, and show God's love by extending mercy where undeserved.  (And isn't that what the central message of Christianity is all about?  Showing love and mercy where it's not deserved?)