The age of the tabletcomputer is upon us, and Wall Street stepped up its efforts this week to gauge just how destructive the trend will be to the traditional personal-computer market.

Computer-industry observers have been warning for months now that tablets are primed to 'crowd out,' or cannibalize, personal-computer sales because they can perform a lot of the same tasks but are cheaper and fit better with an on-the-go lifestyle.

The industry has only a few ofthe slate-style computers on offer at the moment, most prominently Apple's (ticker: AAPL) iPad and Samsung Electronics' Galaxy Tab.

But dozens of companies have announced or are expected to releasetabletcomputers of one sort or another in the coming months, ranging from Archos, a maker of chunky, brick-like portable video players, to ViewSonic, a maker of computer monitors.

The CEO of Acer, currently No. 2 in PC sales, was quoted on Friday boasting the company will dominatetablet sales a couple of years from now.

And so the Street has been busy assembling models: On Monday, Citigroup's team of analysts covering computers, software and semiconductors put out a report saying there will be 35 million tabletcomputers sold in 2011, with Apple's iPad accounting for three quarters of the total, compared with almost 400 million PCs sold.

While the tablet sales look small by comparison, those 35 million sales will eliminate about 11 million PC sales that normally would be expected next year, enough to reduce the PC's sales-growth rate to 9% next year from an original 12% estimate, the Citi team said.

But Citi's estimates may be too kind to the PC. Craig Berger, who follows Intel (INTC) for FBR Capital Markets, gave a more aggressiveestimate on Monday, with 40 million tablets sold by Apple next year and 30 million by the rest of the pack.

Berger warns that the economics of tablet computing are 'not good for PCs,' with one PC sale lost for every 2.5 tablets sold.

And even Berger's numbers may be too low: On Tuesday, a report by the trade magazine DigiTimes said Apple's manufacturer for iPads, Foxconn Electronics, was expanding capacity in China to produce up to 70 million iPads a year.

A report by the same publication on Wednesday predicted that, on top of Apple's output, up to 30 million tabletcomputers would be shipped next year by other manufacturers.

While it's debatable how much each tablet sale steals from what would be a PC purchase, there's no arguing with numbers that have shown a drastic drop-off in personal- computer sales in the third quarter from the first two quarters of the year.

Gartner last month reported that third-quarter sales of laptop computers to consumers was 'the weakest in the last several years.'

Hewlett-Packard (HPQ) gave the latest evidence of the slowing this week, saying laptop revenue fell 3% in the quarter from a year earlier, while overall consumerrevenue was off 10%.