Estate agency has lasted longer than anyone was expecting but a wave of innovation in the sector could soon see most traditional agents swept away by online firms, a prominent Guardian journalist has suggested.

In a column inspired by the fall in the price of Countrywide’s shares and the continued rise in the value of online rival Purplebricks, Guardian Money editor Patrick Collinson said that the relative direction of the two firms “tells you all you need to know about where estate agency is heading”.

He said: “Countrywide could, just about, cope if its problems were purely cyclical. Transaction activity, more important to estate agents than rising house prices, has fallen significantly in the crucial London market. The volume of sales is down, and the time it takes to close a sale is rising.

“Meanwhile, the long boom in letting agency income is over. Rents are flat or falling and buy-to-let activity in 2018 is expected to be one-third the levels of 2015, squeezed by rising taxes and tougher mortgage lending criteria.

“Estate agency has survived longer than anyone expected. We don’t know if it will be Purplebricks or another challenger that will be the ultimate winner in online home selling. What we do know is that the dam has broken and only the upmarket estate agents in the luxury and country home market are likely to survive the onslaught.”

Commenters on the article were quick to point out that while Collinson had made mention of Purplebricks’ fixed fee of £849, he hadn’t explained that it was payable whether a seller’s house actually sold or not.

They also shared their experience of using estate agents, whether online or traditional estate agents, with mixed views on both.