Acquihires are not that much of a problem in London. There are a lot of talented people available for hire, and for a Google or an Amazon, it'll be more productive to poach great software engineers from the financial services world (you probably don't even need to pay them as much as a bank would) than to pay massive premiums by acquiring startups.
You have been at Google, Salesforce.com, Yahoo! for years. You have worked faithfully. Evenings. Weekends. Year in, year out. You have shipped to hard deadlines. You've done the death-march projects. In the trenches. You got the t-shirt. And maybe got called out for valor at a big company gathering. They gave you an extra 2 days of vacation for your hard work.
And that prick sitting in the desk next to you who joined only last week now has $1 million because he built some fancy newsreader that got a lot of press but is going to be shut down anyways.
What kind of message does that send to the party faithful who slave away loyally to hit targets for BigCo?
I'll tell you what is says.
It says if you want to make "real" money - quit.
One of the trickiest things as a business owner is to think through the unintended consequences of incentive schemes that you put in. It sounds like large companies need to do some thinking there too.
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