I'm searching for a large sample dataset (ideally in csv format) which has lat/lng coordinates.

PostgreSQL,PostGIS

One lining will create the data in sql:

test=# select POINT(random()*180-90, random()*90-45)from generate_series(1,5);
                point                 
--------------------------------------
 (79.7833853960037,27.2689918940887)
 (27.6489242445678,-9.43540174048394)
 (-51.9591500423849,19.2025181371719)
 (83.5859301500022,31.8948447704315)
 (-56.1149036698043,42.5037826504558)
(5 rows)

You can easily add this question for an place statement and add the best Postgis function for that geometry if required. Last number '5' obviously controls the number of lines is going to be produced.

Simulations of database activity according to random data will not be sensible, so be skeptical associated with a load or query testing you need to do by using it. Should you really want good examples of real coordinates, the information sets available from OpenStreetMap are extremely large. Posting the TIGER/Line Shapefiles is among the best single teams of sample data such as this around, and it is most likely simpler to cope with compared to people that are transformed into OSM formats.

Following my comment, this can be used html page to create as numerous points as you would like.

<!DOCTYPE html>
<html lang="en-au">
<head>
    <meta charset="utf-8">
    <meta http-equiv="pragma" content="no-cache" />
</head>
<body>
<script type="text/javascript">
function generatePoints(){
    var pointsToGenerate = document.getElementById('pointsToGenerate').value;

    var output = '';

    for (i=0;i<pointsToGenerate;i++) {
        var multiplier = 10000;
        var latitude=(Math.random()*(90*multiplier))/multiplier;
        var longitude=(Math.random()*(180*multiplier))/multiplier;
        latitude *=(Math.floor(Math.random()*2) == 1)?1:-1;
        longitude *=(Math.floor(Math.random()*2) == 1)?1:-1;
        output = output + latitude + ',' + longitude + '\n';
    }

    document.getElementById('output').innerHTML = output;
}
</script>
<input type="text" id="pointsToGenerate" value="1000" />
<input type="button" onclick="generatePoints()" value="Generate Points" />
<div><textarea cols=40 rows=10 id="output"></textarea></div>
</body>
</html>