Right, I've done my trawl of blogs and news sources, and so now I think I have some kind of half-decent perspective on what happened last night. I am not a psephologist, and I haven't looked at every single election result, but the the impression I've got from the coverage I've seen makes it look to me like there has been a kind of reversion to non-national politics. By this, I mean that rather than the electorate voting according to a more or less national set of characteristics - socio-economic class would be the prime example - for national political parties, as was generally the case from 1945 at least onwards, the electorate has voted according to local conditions. To put it another way, whereas one would have once expected people with similar socio-economic status - in England at least, which does contain the vast majority of the British population - to vote for the same party regardless of which constituency they lived in, that hasn't been the case this time round. Swings have not been uniform nationally, and quite specific regional patterns seem to be appearing.
Linton's near-loss actually seems to be typical for a certain kind of London seat, where there is a sitting Labour MP, and the area has both pockets of wealth and of deprivation. In such seats, the sitting Labour member has lost ground to both main parties, something in the region of 8-10%. The effect of the MP's voting record seems to be fairly small, as a matter of fact, which I find disappointing. For example, Glenda Jackson in Hampstead and Highgate haemorrhaged votes to the LibDems, presumably the challengers for leftish votes in these kinds of constituency, despite the fact that she has fairly consistently opposed the government on the kinds of things disillusioned Labour supporters don't like. Especially in the poorer of these seats, the LibDems are increasingly becoming the second party, which might be a good thing by dragging Labour to the left, because they wouldn't have to compete against the Tories, although on the other hand, it could drag Labour to the right, in order to pick up the now-useless Tory votes.
Looking at Linton's result in detail, what has caused him to nearly lose his seat is, assuming consistent voting preferences, roughly the same electorate, and so on, the loss of votes to parties to his left. From 2001, there has been a 4.5% increase in turnout - around four thousand more voters. The LibDems and the Greens each gained about one and a half thousand votes, the Tories gained about three thousand, and Linton lost about two thousand. Assuming that switches from Labour to the LibDems and the Greens are more likely than from Labour to the Tories, and those who could be bothered to vote for Linton last time probably voted this time, the two thousand votes Linton lost probably made up most of the LibDem and Green gains. The Tory gains, on this logic, are people who probably didn't vote at all last time. Thus in this case, if these assumptions hold, Labour nearly lost the seat to the Tories because it - whether at the national level or that of the candidate - was insufficiently left-wing. A look at other, similar, London constituencies indicates a similar pattern. Putney, which Labour did lose, saw the Labour candidate Tony Colman's vote drop by around two thousand, and the LibDems and the Greens gain about two thousand, while votes cast rose by a bit more than two thousand, and the Tories gain about that.
Whether my impression that a kind of non-national politics in the sense I mentioned earlier is true depends on whether the kinds of trends I've hypothesised in a couple of London seats are consistent with results elsewhere. To be honest, I haven't got the patience to do the legwork to find out, so that's your lot for the time being.