The guy said that he wanted 70p to buy a bus ticket home, and one woman gave him some money. I didn't see how much, but he then said that he needed £2 to pay for a bed for the night and asked her if she could spare him any more money. (Based on this, I'm assuming that she gave him the 70p he was initially asking for.) She said no, and he moved on to other people. What's interesting is that he then asked them for 70p for a bus ticket, even the people who were standing right next to the woman who'd just given him money!
Nobody else gave him any money, so he moved to the next bus stop along the road. However, a different woman then hurried after him and gave him a bus pass. She came back, and a minute later he followed, asking what today's date is. She said "It's the 26th of August, and that bus pass is valid until midnight." He looked down at it and said "Oh". As he walked past, I heard him mutter "Could've been a weekly." Based on his tone of voice, he seemed to be resentful that it was such a small gift. He then moved on to ask other people for money, although I didn't hear what he said to them.
The pattern here reminds me of the girl who conned me out of £400: start by asking for something small, then move up to something bigger, even if this creates inconsistencies. (In her case she went back on her claims that "this will be the last thing I ask you for", and in his case it seems odd that he'd need money to go "home" if he doesn't have a place to spend the night.)
Sadly that wasn't the first time I fell for a scam like that. When I was an undergrad, I lent £70 to a guy at Newcastle station who said that the cashpoint machine had eaten his card and he needed to buy petrol to drive his car back home to Scotland. This was on a Saturday, so the banks wouldn't be open again until Monday. This was also before I had a car, so I didn't know much about mileage or petrol costs, but the predicted cost did keep ratcheting up while we walked from the station to the cashpoint. He did show me a recent bank statement from his uncle's restaurant (with a high balance) to prove that he was good for the money; in retrospect I probably should have been more concerned about the fact that it was a photocopy and the address appeared to have been Tippex-ed out on the original. Really, I just felt sorry for him: he said that he'd phoned his father to ask what to do, and it seemed a bit pathetic that someone 10 years older than me would be so much less independent. Needless to say, he never repaid the money.
Nowadays I tend to be a bit more suspicious when people ask me for money, even when it sounds plausible. ("I just need an extra 37p to buy a train ticket!") Events like this do make me a feel a bit better about that attitude, although I realise that it could be completely unrepresentative and the existence of con-artists doesn't preclude the possibility of people begging because they are genuinely in need.
Mind you, in some cases it's quite easy to spot the liars. I remember a guy in Highgate who always wanted "spare change for a pint of milk". However, I never saw him with milk, and he was normally holding a beer can while he asked for money, so I think it's fair to say that he really wanted the money for booze.
As a related issue, I often see people outside East Croydon station asking whether anyone's finished with their travelcard. Leaving aside the legal issues (travelcards are non-transferrable), there are three practical reasons for me to say no:
a) That's not the end of my journey, since I take the bus home from there.
b) Even if it was, I buy monthly travelcards so I'll need it again the following day.
c) Even if was the end of my journey and the end of the month, my travelcard is on Oyster so I'll re-use that physical card when I renew it.
I would explain this to the people who ask, but I doubt that they'd remember me in the future and I don't want to keep repeating all that every day.