Dan Primack of PEHUB posted on what seems to be a growing trend amongst Venture firms; raising 'Annex funds'. In the post, he cited prestigious firms such as Kleiner, Mohr Davidow, Tallwood and First Round Capital all going down this route.
Venture firms usually seek to raise annex funds when the world changes mid-fund, causing a change in their investment thesis or in execution strategy. Such changes most often are symptoms of a firm finding, for whatever reason, they have insufficient capital to carry out their stated initial mission.
In today's market, it would be reasonable to assume that VC's (and the list is surely much broader than these organizations) are faced with a dual market reality of portfolio investments taking a longer period of time to be self-supporting and finding a paucity of like minded firms sufficiently interested in leading follow-on rounds. This double whammy means that prudent firms ought to provision reserves, to support their portfolio, at much higher rates than budgeted. An Annex alternative would be to either reduce the breadth/depth of new investments (e.g. strategy change), or deeply triage existing investments (perhaps prematurely). These actions 'create' more reserves for surviving portfolio investments.
We were last confronted with firms raising Annex funds when the internet only bubble burst. Unfortunately, I don't think many of these funds did well for their LP's. Though, that was before many of these experienced managers garnered experience riding the storm.