It has long perplexed me that so many have used the Widow's Mite to teach on sacrificial giving & obedience [even tithing!]. The issues at hand are not just about extracting a nice story about a women who gives up everything in obedience to the law [or interpretations of that law!]. Rather it is about how to understand this episode within a narrative context that stretches back to Jesus denouncing the scribes for their exploitation of widow's so that their status may be enhanced and upheld. The episode also stretches forward to Jesus' exit of the temple and an announcement of judgement upon the whole temple system.
Commentators such as Lane & Gundry have held that the widow is exemplary of sacrificial giving and is to be commended for her obedience. They contrast the righteousness of the scribes compared with that of the widow. While I admit there is certainly a contrast - this does not seem to be the primary concern of Mark's pericope.
Their interpretation flies in the face of the context, both narrative and [dare I say], historical. In our story, the widow holds nothing back but sacrifices her very life [Βιον]. And for what? So that the religious elite can look flash in their fancy outfits. So that they can have the best seats at their exclusive gatherings. And so that they can enjoy the best, the finest at the banquets they have. And what becomes of this widow’s life? What becomes of all that she had? It is sacrificed to feed their greed. So what becomes of her?
The options are many and varied. Maybe she becomes a hooker to support herself. Maybe she becomes a beggar? Possibly a servant, or worse a slave? Maybe she has a rich brother who will take her in and care for her needs. Maybe she will be lucky enough to find another husband who will support her. Or maybe she will end up like many others - marginalized and extricated.
Fitzmyer reminds us that in Mark Jesus asserts that human needs take precedence over religiosity (as seen in 3:1-5 [healing on the Sabbath], 7:10-13 [the qorban tradition, by which elderly parents may be denied support from their adult children], and 12:28-34 [where loving God and neighbour is worth more than burnt offerings]). He concludes: “given such a reaction of Jesus in other parts of the Marcan Gospel, would the Marcan Jesus become enthusiastic about and praise the widow’s contribution, when it involved ‘all that she had to live on’? The Corban-saying seems to set limits to the interpretation of Jesus’ words in this episode. With the Markan context in mind, Wright says “Her religious thinking has accomplished the very thing that the scribes were accused of doing… She has been taught and encouraged by religious leaders to donate as she does, and Jesus condemns the value system that motivates her action.”
It appears to me that Mark often sets up Jesus as teaching, and then directly offers a situation that illuminates and explains the teaching in concrete details. In 1:14-20 Jesus teaches the Kingdom & calls disciples; 1:21-27 exorcises demons and the crowds are amazed at his teaching & authority; 1:39-40 Jesus goes about teaching and then heals. The list goes on, so that when we get to 12:38-13:2 it seems almost natural to see this as the patter Mark has set: teaching/announcements with a concrete example that demonstrates and explains what has been said. As Belo has noted: “The Messiah is occupying the temple and holding a protest meeting against the dominant ideology.” Thus, in both word and praxis which mutually interpret each-other.
So given this info, is Jesus commending the widow's sacrifice or merely using this scenario as a concrete example of scribes who rip off people so that they can enjoy the finer things in life - with the prestige that it offers? Why would Jesus commend this woman for supporting a system that ultimately leads to her demise? And why would Jesus leave the temple courts, with a pronouncement of Judgement on the Temple? These rhetorical questions should offer us a definitive understanding of Mark 12:38-13:2 and what Jesus meant to convey.
 Fitzmyer, Luke, 2:1321
 Wright, A. G. “The Widows Mites: Praise or Lament? – A Matter of Context” CBQ 44  256-65. See also C. A. Evans Mark 8-16 who concurs with Wright.  Belo, F. A Materialist Reading of the Gospel of Mark [Orbis, 1981] pg. 192----------------------------------------------------------------------------------------
Post-ScriptThere appears to be some good discussion on the radical nature of Jesus' announcement and call: See Ben Myers, Privileged westerners and the call of Jesus and Michael Jenson, "Jesus the exemplar": what could that mean?