Google (NASDAQ:GOOG) sent out an email this week reminding users that the death of the Google Wave, its Web-based collaborative editing service, is near. Wave will shutter for good on April 30, following less than three years of lackluster existence.

The service will remain available in read-only mode until that date, allowing users to export PDF copies of needed conversations. Wave’s failure follows a string of product shutdowns for the search giant and has led to speculation about when, or if, a similar email about social networking service Google+ will be sent out in the future.

Wave launched in 2009 as an invitation-only beta — a rollout style common for Google products. Early adopters struggled with the collaboration tool, questioning what its purpose was and whether its functions weren’t better provided by pre-existing tools. The closure of Wave was initially announced in 2010 but the service inexplicably held on until now.

Wave occasionally fell victim to easy jokes, as when Google misspelled the name of the service as Google Wage in the latest official email.

Not the first, and it won’t be the last, product to disappear

Google has been on a project-shuttering streak over the past six months. Buzz, the company’s first attempt at social networking, met its demise in December after a year and a half of service. The impending end of photo sharing and editing site Picnik was announced in January. The same announcement ended relatively little-known services including Needlebase, Urchin, and Google Sky Maps.

Trimming the fat is a positive move, but also a somewhat puzzling one in view of Google’s insistence on doubling down on the foundering Google+. The company recently announced plans to double the Google+ user base, which Google says now stands at 90 million users, before the end of the year.

So far, it’s not clear marketing efforts on behalf of the service have helped. Google+ was launched with a closed beta that dragged on so long that many of the early adopters lost interest. Research firm comScore found that Google+ users average a mere three minutes on the site per month, whereas Facebook users average almost seven hours a month on that site. It’s also not clear how many users ended up with a Google+ profile by default, since in late Janaury Google+ registration became automatic for those who signed up for Gmail, YouTube, and Blogger.

Google endured criticism for designing its Search Plus Your World optional search tool to favor relevant Google+ profiles, although the use of Search Plus optional. But that is small beer compared to the puzzlement by some in the tech industry over Google’s dogged pursuit of social networking success.

One of the most high-profile assessments of the issue has come from former Google executive James Whittaker, now with Microsoft (NASDAQ:MSFT). Whittaker posted a blog on the Microsoft site last week explaining why he left Google. In the process, he took Google co-founder Larry Page to task for, he said, diminishing the company’s innovative spirit in favor of a competitive battle with Facebook. Whittaker wrote, “The Google I was passionate about was a technology company that empowered its employees to innovate. The Google I left was an advertising company with a single corporate-mandated focus.”