overexposure to the same old grape varieties can dull the palate and provoke a sense of deja vu - as in "I'm sure I've had that sauvignon before".
You might not recognise the bottle or remember whether it came from Asda, Tesco or Morrisons, but it certainly tastes the same. With its aromas of cut grass and gooseberries it shouts New Zealand, though it could be a New Zealand lookalike from Chile, South Africa or even France.
You almost wonder if each country ships its sauvignon in bulk and it all gets tipped into a vast tank from where it can be pumped off to the bottling line and be slapped with a different label each time. If so, you could say the same about a lot of the pinot grigio, chardonnay, merlot and shiraz that clogs up the shelves.
There is an antidote to mono-varietal monotony however, and it's called Portugal, where they believe in weird and wonderful blends of local grapes like alfrocheiro, fernao pires, viosinho and bastardo. The only one with any recognition at all is tourigal nacional, but it covers a mere 6% of the vineyards. With a lack of international varieties, or well-known regions like Rioja, or recognisable brands -apart from that fading 1970s superstar Mateus Rose - the country punches well below its weight, reckons Nick Oakley.
As a long-established Portuguese wine importer, he spent years bashing his head against a brick wall, with the trade not interested in listing stuff that no-one asked for. He doesn't have a drop of Portuguese blood in his veins, or a Portuguese wife, and began to wonder why he bothered. All he had was an unswerving belief in the quality of the country's wines.
Two years ago the wall began to crumble, with retailers like Great Grog in Edinburgh, who never previously stocked a single bottle, now embracing Portugal with a vengeance. Though it takes a leap of faith to buy some obscure blend of unpronounceable grapes, it's usually worth it. The only really duff one I can remember was a syrupy, overpriced plonk from Cliff Richard's Vida Nova estate in the Algarve.
Initially people began to embrace the easy-drinking wines of the Alentejo in the south, made in a style which Oakley calls "fruit soup", often with a dollop of sauvignon or cabernet to make them less scary. But the real heart and soul of Portuguese wine lies further north beyond the Serra de Estrela, or mountains of the stars. Here in regions like Dao, the Douro and the Minho - home to vinho verde - the cool, damp influence of the Atlantic really makes itself felt.
The best advice on how to get into Portuguese wine is to forget about grapes and simply remember those three regions, particularly the Dao, especially in that congested sweet spot from £6-£10. The vineyards, high up on granite slopes, are cooled by the breeze off the sea and the night air coming down from the mountains. The effect is to freshen up the wines and give the reds a lovely savoury, food-friendly edge.
As home to port, the country's national drink and the oldest demarcated wine region in the world, the Douro will always be more famous, but personally I am drawn to the Dao and the new generation of dry, unfizzy vinho verde.